 # Slope – Intercept Form What do all the points on the y-axis have in common? What do all the points on the x-axis have in common?

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Slope – Intercept Form What do all the points on the y-axis have in common? What do all the points on the x-axis have in common?

Slope-Intercept Form of a Linear Equation
We can use the x- & y-intercepts (where the line crosses the x- & y-axes, respectively) to graph a linear equation: 2x + 3y = 6 Find the y-intercept by setting x = 0 & solving for y. 2(0) + 3y = 6  3y = 6  y = 2  (0,2) y-intercept (2) Find the x-intercept by setting y = 0 & solving for x. 2x + 3(0) = 6  2x = 6  x = 3  (3,0) x-intercept (3) Draw the line of the linear equations connecting the points (x-intercepts, 0) & (0, y-intercept). Connect points (0,2) & (3,0) w/ a line.

Slope-Intercept Form of a Linear Equation
Slope-intercept form: y = mx + b, where m = slope, b = y-intercept. To find the slope-intercept form of a linear equation, given 2 coordinates: (-3,1) & (2,-1) Find slope of the line. Slope = (y2 – y1) / (x2 – x1) = [(-1) – (1)] / [(2) – (-3)] = -2/5 (2) Use one of the coordinates to find y-intercept. (-3,1)  1 = (-2/5)(-3) + b  1 = 6/5 + b  b = 1 – (6/5) = -1/5 (3) Write equation using slope & y-intercept. y = (-2/5)x + (-1/5) OR y = (-2/5)x – (1/5)

Classwork (HW if not completed in class)
Think & discuss – p. 552 Describe the line represented by the equation y = -5x + 3. Give a real-life example with a graph that has a slope of 5 and a y-intercept of 30. Classwork (HW if not completed in class) p. 552 – ex (evens), 21, 22, 24, 26, 28-30

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