Question

In the parallelogram below, AB=2x+8 and CD=5x-1. What is the length of AB?

Answer 1

AB = CD

BC = DA

Explanation:

Since 3x+2 = 5x-2, solving for x yields 2. Since BC = 4x+1 = DA, BC and DA both equal 4(2)+1 = 9.

Answer 2

AB = 14

Explanation:

Lines AB and CD are opposite each other and as the shape is a parallelogram, they are of equal length:

AB = CD

2x + 8 = 5x - 1

Add 1 to both sides to isolate the 5x:

2x + 8 + 1 = 5x - 1 + 1

2x + 9 = 5x

Subtract 2x from both sides to isolate the 9:

2x + 9 - 2x = 5x - 2x

9 = 3x

Divide both sides by 3:

9 ÷ 3 = 3x ÷ 3

x = 3

As AB = 2x + 8, plug the known variable x in:

2x + 8

2(3) + 8

6 + 8

= 14

Hope this helps!