7.因式分解5x(x
5x(x-y)+2y(x-y) 2a(a-b)-4b(b-a) -8a(a-2b)^3+2a^3(2b-a)2 10a(y-x)+5b(y-x) 4x^2+4xy+y^2 9x^2+6xy+y^2 25x^4-10^2+1 9a^4-81b2 36X^2-84xy+49y^2 x^2+8xy+16y^2
5x(x-y)+2y(x-y)=(x-y)(5x+2y) 2a(a-b)-4b(b-a)=2(a-b)(a+2b) -8a(a-2b)^3+2a^3(2b-a)2=-2a(a-2b)^2(4a-8b+a^2) 10a(y-x)+5b(y-x)=5(y-x)(2a+b) 4x^2+4xy+y^2=(2x+y)^2 9x^2+6xy+y^2=(3x+y)^2 25x^4-10^2+1=(5x-1)^2 9a^4-81b2=9(a^2+3b)(a^2-3b) 36X^2-84xy+49y^2=(6x-7y)^2 x^2+8xy+16y^2 =(x+4y)^2