Geometry Proof - Please Help - Thanks!

Question

Algebra The length of the base of an isosceles triangle is x. The length of a leg is 2x - 5. The perimeter of the triangle is 20. Find x.

Know

1. What is the perimeter of a triangle?

2. What is an isosceles triangle?

Need

3. What are the sides of an isosceles triangle called?

4. How many of each type of side are there?

5. The lengths of the base and one leg are given. What is the third side of ?

Plan

6.  Write an expression for the length of the third side.

7.  Write an equation for the perimeter of this isosceles triangle.

Solve

8.  Solve the equation for x. Show your work.

Answer 1

2(2x-5)+x = 20

4x - 10 + x = 20

5x - 10 = 20

5x = 30

x=6

The isosceles triangle has lengths 7,7, and 6