помогите решить !!!!!!!!!!!!!!!
(4a-1)(4a+1)+(9+a)(a-9)
(5x-7y)(5x+7y)+(7x-5y)(7x+5y)

16а^2-1+а^2-81=17а^2-8225х^2-49у^2+49х^2-25у^2=74х^2-74у^2

1)=(4а)²-1²+а²-9²=16а²-1+а²-81=17а²-822)=(5х)²-(7у)²+(7х)²-(5у)²=25х²-49у²+49х²-25у²=(25х²+49х²)-(49у²+25у²)=74х²-74у²