Unit 3 - Writing equation of a line (slope-intercept form)

Writing the equation of a line (slope-intercept form)

Aim: How can we write the equation of a line in slope-intercept form?

Multiple Choice

Write the equation of the line shown on the graph.

• A

• B

• C

• D

Write the equation of a line given slope (1/2) and a point on the line (2, 5).

• y = mx + b

• y = (1/2)x + b

• Substitute the values for x and y into the equation. Solve for b (y-intercept).

• 5 = (1/2)(2) + b

• 5 = 1 + b

• 4 = b, or b = 4

• Rewrite the equation in slope-intercept form. y = 1/2(x) + 4.

Multiple Choice

Write the equation of the line.

• A

• B

• C

• D

Multiple Choice

Write the equation of the line.

• A

• B

• C

• D

Line goes through (1,2) with a slope of 7.

• y = mx + b

• y = 7x + b

• Substitute the ordered pair (1,2) in place of x and y.

• 2 = 7(1) + b, Solve for b.

• 2 = 7 + b, Subtract 7 from each side.

• 2 - 7 = -5, b = -5

• y = 7x - 5, check algebraically or using desmos!

Line goes through (3, -1) with a slope of -1

• y = mx + b

• y = -1x + b

• Substitute the ordered pair (3,-1) in place of x and y.

• -1 = -1(3) + b, solve for b.

• -1 = -3 + b, add 3 to both sides.

• -1 + 3 = 2, b = 2

• y = -x + 2 OR y = -1x + 2

Line goes through (-2,5) with a slope of - 4.

• y = mx + b

• y = -4x + b

• 5 = -4(-2) + b

• 5 = 8 + b

• 5 - 8 = -3, b = -3

• y = -4x - 3

• Check algebraically or graphically using desmos!

Line goes through (2, -4) with a slope of -1.

• y = mx + b

• y = -1x + b

• -4 = -1(2) + b

• -4 = -2 + b

• - 4 + 2 = -2, b = -2

• y = -x -2 OR y = -1x - 2

• Check algebraically or graphically using desmos!

Open Ended

1. How can we write the equation of a line in slope-intercept form given the slope of the line and one point on the line?

2. Explain the meaning of slope as it relates to the real-world.