(a-5)²-2(a-5)(a+5)+(a+5)² при a=-4/9

Question

(a-5)²-2(a-5)(a+5)+(a+5)² при a=-4/9

Answer 1

(a-5)²-2(a-5)(a+5)+(a+5)² =((a-5)+(a+5)) ²=(2a) ²=4а²

При a=-4/9   4*(-4/9)²=4*16/81=64/81