Q&A for How to Solve Systems of Equations

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  • Question
    What is the value of two numbers if their sum is 14 and their difference is 2?
    Donagan
    Top Answerer
    x + y = 14. x - y = 2. Add the two equations together: 2x = 16. x =8. 8 - y = 2. y = 6.
  • Question
    How do I draw the straight line of y = x2 - 7x + 12 and find zeroes of it?
    Donagan
    Top Answerer
    y = x² - 7x + 12 = (x - 3)(x - 4). This is a parabola, not a straight line. To find the zeroes, set (x - 3)(x - 4) equal to zero. That means either (x - 3) or (x - 4) must equal zero. If (x - 3) equals zero, x has to equal 3. If (x - 4) equals zero, x has to equal 4. So the zeroes are 3 and 4.
  • Question
    How do you do 2x+y=10, 3x-4y=47?
    Community Answer
    Use the elimination method. First multiply the first equation by 4: 8x + 4y = 40. Now add this equation to the second equation above. The +4y and the -4y cancel each other to eliminate the y term, leaving 11x = 87. Divide both sides by 11: x = 87/11. Now plug this x value into either original equation: 2(87/11) + y = 10. So 174/11 + y = 10, and y = 10 - 174/11 = 110/11 - 174/11 = -64/11. So x=87/11, and y = -64/11. Unwieldy, but there it is. Check the answer by substituting the x and y values into either of the original equations to see if they work. (They do.)
  • Question
    If a system of equations has no solution, what does the graph look like?
    I_l1ke_gam3s
    Community Answer
    The lines will be parallel, meaning they will never intersect. That is what "no solution" really means.
  • Question
    Is linear equations hard?
    I_l1ke_gam3s
    Community Answer
    It can be, but with time and practice, it will be super easy to solve any type of systematic equation question.
  • Question
    Solve for x in 2x = y - 5.
    I_l1ke_gam3s
    Community Answer
    Because you have two variables in one equation, all you can do is solve for x in terms of y. x = (y - 5) / 2.
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