Q&A for How to Find the Y Intercept

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  • Question
    How do you find the x-intercept in y = mx + b?
    David Jia
    Academic Tutor
    David Jia is an Academic Tutor and the Founder of LA Math Tutoring, a private tutoring company based in Los Angeles, California. With over 10 years of teaching experience, David works with students of all ages and grades in various subjects, as well as college admissions counseling and test preparation for the SAT, ACT, ISEE, and more. After attaining a perfect 800 math score and a 690 English score on the SAT, David was awarded the Dickinson Scholarship from the University of Miami, where he graduated with a Bachelor’s degree in Business Administration. Additionally, David has worked as an instructor for online videos for textbook companies such as Larson Texts, Big Ideas Learning, and Big Ideas Math.
    Academic Tutor
    Expert Answer
    Find the x-intercept by plugging in 0 for the value of y. The x-intercept will equal whatever value comes out at the other end of the equation.
  • Question
    What do you mean by x-intercept in math?
    David Jia
    Academic Tutor
    David Jia is an Academic Tutor and the Founder of LA Math Tutoring, a private tutoring company based in Los Angeles, California. With over 10 years of teaching experience, David works with students of all ages and grades in various subjects, as well as college admissions counseling and test preparation for the SAT, ACT, ISEE, and more. After attaining a perfect 800 math score and a 690 English score on the SAT, David was awarded the Dickinson Scholarship from the University of Miami, where he graduated with a Bachelor’s degree in Business Administration. Additionally, David has worked as an instructor for online videos for textbook companies such as Larson Texts, Big Ideas Learning, and Big Ideas Math.
    Academic Tutor
    Expert Answer
    The x-intercept is just wherever the graph crosses the x-axis (the straight, horizontal line that cuts through the middle of the graph).
  • Question
    If I have (3, -12) as my points and an x-intercept of one, what would the y-intercept be?
    Donagan
    Top Answerer
    Solve by using Method 2 above. You need two points to use that method. One point is given as (3,-12). The second point is the given x-intercept, which is (1,0).
  • Question
    If I am only given one specific point, how can I convert it into slope intercept form?
    Technist
    Community Answer
    You can't have only one point. Imagine you're standing in the middle of your neighborhood street and have no where to go. No direction, no distance, etc. You don't need to go to your friend's house or to school. That is an example of having only one point without any other point to go to so there's no line. Thus, no equation. And more importantly, no math to work out.
  • Question
    I do not get the last part of method 2, can you explain?
    Donagan
    Top Answerer
    Using the "slope-intercept" form of the line's equation (y = mx + b), you solve for b (which is the y-intercept you're looking for). Substitute the known slope for m, and substitute the known point's coordinates for x and y, respectively, in the slope-intercept equation. That will let you find b. In the example in Method 2, the calculated slope is -3, so m becomes -3. The known point is given as (1,2), so x in the equation becomes 1, and y becomes 2. Thus, the slope-intercept equation becomes 2 = -3(1) + b. So 2 = -3 + b, and b = 5. That's the y-intercept.
  • Question
    What do I do if the only thing on the other side of the = is a variable?
    Donagan
    Top Answerer
    If you mean that the only thing on the "x" side of the equation is x (so that y = x), that indicates a slope (m) of 1 and a y-intercept (b) of zero.
  • Question
    How do I find the y intercept when it is not numbered and obviously a decimal?
    Community Answer
    Assuming by numbered you mean whole number, it doesn't matter, the method is the same in both cases.
  • Question
    How do I find the y-intercept if 3x - y = 6?
    Community Answer
    The graph crosses the y-axis when x=0, so substitute 0 for x in this equation, and solve for y: y is -6. Since y is -6 when x is 0, the y-intercept is -6.
  • Question
    How do I find the y-intercept if the only given information is the slope and no graph or point(s) specified?
    Donagan
    Top Answerer
    You would have to be given more information than just the slope in order to find the y-intercept.
  • Question
    How do I find the slope for this and then the y-intercept (0,0) and (4,-3)?
    Donagan
    Top Answerer
    The slope has a numerator consisting of the difference between any two x values on the line and a denominator consisting of the difference between the two corresponding y values. In this case the slope is (4 - 0) / (-3 - 0), or 4 / -3, which equals -4/3. The y-intercept is the y-value when x=0. In this case, we are told that the line passes through the point (0,0), which means that the y-intercept is zero.
  • Question
    What if the slope is undefined?
    Donagan
    Top Answerer
    If a slope is said to be "undefined," that means that the slope is infinite, which in turn means that the line is vertical (or parallel to the y-axis).
  • Question
    Where is the y-axis on the Cartesian plane?
    Donagan
    Top Answerer
    The y-axis is the vertical line that passes through the origin. It is the series of all points where x = 0.
  • Question
    What if my problem looks like 4y = 3?
    Aiden Chester
    Community Answer
    OK, let's put the equation into slope-intercept form (y = ax+b), where we know b is the y-intercept. If we divide both sides by 4, then we get y = 3/4. There are 0 x's, so ax = 0x. That leaves us with y = 0x+3/4, where b = 3/4. This does make sense, because 0x would just cancel out to 0, leaving us with our original equation of y = 3/4. If b is the y-intercept value, then the y-intercept is at (0, 3/4)! You can check a graph of y = 3/4 to make sure.
  • Question
    How do I find the y intercept when my equation is y=3x+b. How do I find b?
    I_l1ke_gam3s
    Community Answer
    You need to have a given point on the line, so you can substitute values for y and x to find the value of b.
  • Question
    How do I find the intercept on the equation 4x - 3y - 24 = 0?
    I_l1ke_gam3s
    Community Answer
    If you want to find the y-intercept, set x = 0. 4(0) - 3y - 24 = 0, or -3y - 24 = 0. Add 24 to both sides: -3y = 24, so y = 24/-3 = -8, and -8 is the y-intercept.
  • Question
    How do I find the y-intercept in y=3x×16?
    I_l1ke_gam3s
    Community Answer
    3x(16) = 48x. So you have y = 48x. The y-intercept is zero because y=48x + 0.
  • Question
    What is the y-intercept of a line with a slope of -3/2 and an x-intercept of (4,0)?
    Community Answer
    Plug the values (4,0) into the slope-intercept form of the equation, y = mx + b, given that m = -3/2: 0 = (-3/2)(4) + b. Then 0 = -6 + b, and 6 = b. So the y-intercept (b) is 6.
  • Question
    y = 1/2. What is the y-intercept and slope?
    Community Answer
    When y equals a constant (such as 1/2), the graph consists of a straight, horizontal line that crosses the y-axis at the value of the constant. So here the line parallels the x-axis, which means its slope is 0, and it intercepts the y-axis at +1/2.
  • Question
    What if there is no y-intercept? ex: 1/3y = -4x and we are trying to write the equation in slope form.
    Community Answer
    A y-intercept occurs when x = 0. In this equation, when x = 0, y = 0. Therefore, the y-intercept occurs at the origin (where the x- and y-axes intersect). If you multiply both sides of the equation above by 3, you get y = -12x. That is the slope form of the equation (y = mx + b) where b = 0.
  • Question
    How do I find the Y intercept when it does not cross or touch the Y axis?
    Community Answer
    In that case, keep counting the boxes until you get to a spot where it would intercept with the y axis.
  • Question
    How do I find the Y intercept if I know the points?
    Community Answer
    Let’s say the points are (2,6) and (-3,-4). Subtracting the y-value of one point from the y-value of the other we get -4-6=-10. Subtracting the x-value of the same point from the x-value of the other, we get -3-2=-5. The slope of the line, m, equals (-10/-5)=+2. So m=2. Remembering that the general equation of a line is y=mx+b, this line’s equation is y=2x+b. We also have the two points given at the beginning and we can use either one to enter the x and y values of the point into the equation, so 6=2(2)+b. So we solve for b. b=6-4=2, which is the y-intercept we were looking for.
  • Question
    Does an answer of zero mean the graph is horizontal?
    Community Answer
    If x were to be zero, then the line would be horizontal. If y is zero, it just crosses through the origin.
  • Question
    if you know the slope how do you find the y intercept?
    Community Answer
    For example, the slope of your line is 2 and a point that goes on your line is (2,6), then substite the values with the equation y=mx+b, where the m is the gradient and the the b is the y intercept. y=mx+b, y=2x+b. Substitute the coordinate points. 6=2(2)+b, 6=4+b. Now, you need to get b alone on one side, so rearrange the equation. 6=4+b, 6-4=b, 6-4=2, 2 is the y-intercept.
  • Question
    If the gradient of a line is -4 and it has an x-intercept of 3, what's the y-intercept of the line?
    Cabbache
    Community Answer
    The equation of a line is y = mx + c where c is the y-intercept. We are given m = -4, so the equation is y = -4x + c. We know that the line has an x-intercept of 3, which means the line passes through point 3,0. This means that when y = 0, then x = 3 so 0 = -4(3) + c. From that we can find c = 7, which is the y-intercept.
  • Question
    How do I find the y intercept when a line passes through the origin if I have x value and slope value?
    Donagan
    Top Answerer
    If the line passes through the origin, that means the y intercept is zero.
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