Answer:
10pix+65pi
Step-by-step explanation:
pi(x+9)^2-pi(x+4)^2
=pi(x^2+18x+81)-pi(x^2+8x+16)
=pix^2+18pix+81pi-pi(x^2+8x+16)
=pix^2+18pix+81pi-pix^2-8pix-16pi
=10pix+65pi
