Question

①(x^2-9)a^2+4^(9-a^2)=_______=________ ②因式分解：（x^2+25)^2-100x

Answer 1

①(a^2-9)a^2+4^(9-a^2)=(a²-9)(a²-4)=(a-3)(a+3)(a-2)(a+2)

②因式分（x^2+25)^2-100x^2 =(x²+25-10x)(x²+25+10x)=(x-5)²(x+5)²

③用因式分解计算：28×32.4^2+56×32.4×67.6+28×67.6^2 =28×(32.4²+2×32.4×67.6+67.6²) =28×(32.4+67.6)²=28×100²=280000