Question

The measure of two sides of a triangle are given. If P is the perimeter, find the measure of the third side. P = 8x²+4x-1.

Answer 1

3x² + 1

Explanation:

The perimeter is the sum of the exterior lengths of a polygon.

Here, the perimeter will be the sum of the lengths of the triangle. Two of them are given: 5x² + x - 4 and 3x + 2. Let's say the third side is A. Then, we know that:

P = 8x² + 4x - 1 = (5x² + x - 4) + (3x + 2) + A

On the right side, we have:

(5x² + x - 4) + (3x + 2) + A

5x² + 4x - 2 + A

This is equal to 8x² + 4x - 1:

5x² + 4x - 2 + A = 8x² + 4x - 1

Solve for A by isolating it:

A = (8x² + 4x - 1) - (5x² + 4x - 2) = 8x² + 4x - 1 - 5x² - 4x + 2 = 3x² + 1

The third side is thus 3x² - 1.