Question

What has she done wrong?

Answer 1

see explanation

Explanation:

Her error is in squaring (2y)²

She has (2y)² = 2y²

when it should be 2y × 2y = 4y²

Then

(2y)² = 6² + 8²

4y² = 36 + 64

4y² = 100 ( divide both sides by 4 )

y² = 25 ( take square root of both sides )

y =
`√(25)` = 5