Question

I need help on number 17 please and number 18

Answer 1

17)

`16\pi(x^2+4x+4)`

18)

`A=\pi (6x+51)`

Explanation:

17)

`S=4 \pi r ^2\\r = (2x+4)\\r^2=(2x+4)^2 = 4x^2+16x+16\\S=16 \pi (x^2+4x+4)`

18)

`A=\pi r ^ 2\\A_(new)=A_(metal)-A_(hole)\\A=\pi((x+10)^2-(x+7)^2)\\A=\pi ((x^2+20x+100) - (x^2 + 14x + 49))\\A =\pi (6x+51)`