Answer:
17)
[tex]16\pi(x^2+4x+4)[/tex]
18)
[tex]A=\pi (6x+51)[/tex]
Step-by-step explanation:
17)
[tex]S=4 \pi r ^2\\r = (2x+4)\\r^2=(2x+4)^2 = 4x^2+16x+16\\S=16 \pi (x^2+4x+4)[/tex]
18)
[tex]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)[/tex]
