Question

Divide z(5z² – 80) by 5z(z + 4)

Answer 1

Dividend `= z(5z^2 – 80)`

`= z[(5 xx z^2) - (5 xx 16)]`

`= z xx 5 xx (z^2 - 16)`

`= 5z xx (z + 4)(z - 4)`     .....[using the identity a² – b² = (a + b) (a – b)]  

z(5z² – 80) ÷ 5z(z + 4) = `(5z(z - 4)(z + 4))/(5z(z + 4)) = (z - 4)`