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SAT Math skill page

SAT Slope-Intercept Form Practice

Read y = mx + b as a story about starting value and rate of change.

Practice slope-intercept form in Dolphin SATPractice questions
10-16 min practice time3 questions on pageAlgebra
Practice time10-16 min
Question bank3 questions
Best forAlgebra

What this tests

What to know for this SAT skill

Dolphin question bank

Practice your skill

Question 1 of 3Easy
In the equation y = 3x + 7, what is the slope?
  1. 3
  2. 7
  3. 10
  4. 21
Show answer and solution
Correct answerA. 3

Solution walkthrough

  1. In y = mx + b, m is the slope.
  2. Here m = 3.
Question 2 of 3Medium
A line has slope -2 and y-intercept 5. Which equation represents the line?
  1. y = -2x + 5
  2. y = 5x - 2
  3. y = 2x + 5
  4. y = -5x + 2
Show answer and solution
Correct answerA. y = -2x + 5

Solution walkthrough

  1. Use y = mx + b with m = -2 and b = 5.
Question 3 of 3Hard
A gym charges $20 to join and $15 per month. Which equation gives total cost C after m months?
  1. C = 20m + 15
  2. C = 15m + 20
  3. C = 35m
  4. C = 15m - 20
Show answer and solution
Correct answerB. C = 15m + 20

Solution walkthrough

  1. The monthly rate is the slope, 15, and the initial fee is the intercept, 20.

Avoid these traps

Common mistakes on this skill

Swapping slope and y-intercept

In y = mx + b, m is the change in y per unit change in x and b is the value of y when x = 0.

Ignoring the sign of the slope

A negative slope means y decreases as x increases.

Study plan

How to practice this skill in Dolphin

  1. Identify two points or the rate and initial value supplied by the problem.
  2. Compute slope as change in y divided by change in x, preserving units.
  3. Find b by using x = 0 or substituting a known point, then verify another point.
Practice slope-intercept form in Dolphin SAT

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FAQ

Questions about SAT Slope-Intercept Form Practice

What does the y-intercept represent?

It is the output when the input is 0, often an initial amount or fixed fee.

How do I find slope from two points?

Subtract the y-values in the same order as the x-values and divide: (y2 - y1)/(x2 - x1).