25(a+b)^2 - 9(a - b)^2 - 知识问答

25(a+b)^2 - 9(a - b)^2

1个回答

25(a+b)^2 - 9(a - b)^2
=[5(a+b)+3(a+b)]*[5(a+b)-3(a+b)]
=[5a+5b+3a+3b]*[5a+5b-(3a+3b)]
=[8a+8b]*[5a+5b-3a-3b]
=(8a+8b)*(2a+2b)
4x^2 - (x^2 + 1)^2
=(x^2+2x+1)*(-x^2+2x-1)
=(x+1)^2*-(x-1)^2

相关问题