Q&A for How to Use the Slope Intercept Form (in Algebra)

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How do you find the y-intercept when you are given two plot points?

Grace Imson, MA
Math Instructor, City College of San Francisco
Grace Imson is a math teacher with over 40 years of teaching experience. Grace is currently a math instructor at the City College of San Francisco and was previously in the Math Department at Saint Louis University. She has taught math at the elementary, middle, high school, and college levels. She has an MA in Education, specializing in Administration and Supervision from Saint Louis University.

Grace Imson, MA

Math Instructor, City College of San Francisco

Expert Answer

One way is to use the slope-intercept form. Use the two points to solve for the slope. Once you have the slope, plug one of the points into the slope-intercept form (y = mx + b). M is the slope, then plug in any coordinate using one of the points. Solve for B. B is the y-intercept.

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Can the y = mx + b formula be reversed to solve for x? If so, how?

Donagan

Top Answerer

Subtract b from both sides, then divide both sides by m. x = (y - b) / m.

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Change the following equation of a line into slope-intercept form: y - 28 = -7x.

I_l1ke_gam3s

Community Answer

Add 28 to both sides: y = -7x + 28. Since y is now isolated, you don't have to do anything else.

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What should I do if the y-value is negative in slope-intercept form?

Community Answer

Multiply both sides of the equation by (-1) to make the y positive.

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