（1）4/9a^2 b^2=（2/3ab）^2（2）16/25（a-b）^4=4/5(a-b)^2]^2 不明白可追问，满意请采纳
4/9*a^2*b^2=(2/3*ab)^216/25(a-b)^4=[4/5(a-b)^2]^2
2/3ab;6/25a^4-64/25a^3b+96/25a^2b^2-64/25ab^3+16/25b^4
