# SAT Math Multiple Choice Question 791: Answer and Explanation

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**Question: 791**

**11.** If the graph of the equation *y* = 5*x* + 3 is shifted down 4 units, what is the *x-*intercept of the new line?

- A. –1
- B.
- C. 1
- D.

**Correct Answer:** B

**Explanation:**

**B**

**Difficulty:** Medium

**Category:** Heart of Algebra / Linear Equations

**Strategic Advice:** You aren't given a graph to shift, so either draw a quick sketch of the given line or mentally picture what happens when the line is shifted. Don't forget-when a linear equation is written in the form *y* = *mx* + *b*, *m* is the slope of the line and *b* is the *y*-intercept (not the *x*-intercept).

**Getting to the Answer:** The graph of the given line has a slope of 5 and a *y*-intercept of 3. Shifting the line down 4 units doesn't change the slope, but the *y*-intercept moves down 4, so the new *y*-intercept is 3 - 4 = -1. Wait, though-choice A is not the correct answer: The question asks for the *x*-intercept of the new line, not the *y*-intercept. The equation of the new line is *y* = 5*x* - 1. Set *y* = 0 and solve for *x*:

This means (B) is correct.