 # Use slope and y-intercept to write an equation

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Use slope and y-intercept to write an equation
EXAMPLE 1 Use slope and y-intercept to write an equation Write an equation of the line with a slope of –2 and a y-intercept of 5. y = mx + b Write slope-intercept form. y = –2x + 5 Substitute –2 for m and 5 for b.

Standardized Test Practice
EXAMPLE 2 Standardized Test Practice Which equation represents the line shown? A y = – x + 3 2 5 B C y = – x + 1 D y = 3x + = The slope of the line is rise run –2 5 2 . The line crosses the y-axis at (0, 3). So, the y-intercept is 3. y = mx + b Write slope-intercept form. 2 y = – x + 3 5 2 Substitute – for m and 3 for b. 5

EXAMPLE 2 Standardized Test Practice ANSWER The correct answer is A. B D C A

GUIDED PRACTICE for Examples 1 and 2 Write an equation of the line with the given slope and y-intercept. 1. Slope is 8; y-intercept is –7. y = 8x – 7 ANSWER

GUIDED PRACTICE for Examples 1 and 2 Write an equation of the line with the given slope and y-intercept. 2. Slope is ; y intercept is –3. 3 4 y = 3 4 x – 3 ANSWER