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## Homework Statement

I can't determine where the 40x comes from.

From: 4x + 5 = 8√(1 - x)

To: 16x^2 +40x + 25 = 64 - 64x^2

## Homework Equations

√1-x^2 = √1-x *√x+1

## The Attempt at a Solution

4x + 5 = 8√(1-x)

4x^2 + 5^2 = (8 - 8x)*(8x + 8)

16x^2 +25 = 64 - 64x^2