16(x+y)²;-25(x-y)²;

16(x+y)²;-25(x-y)²;


=[4(x+y)]²;-[5(x-y)]²;
=[4(x+y)+5(x-y)][4(x+y)-5(x-y)]
=(9x-y)(-x+9y)
=-(9x-y)(x-9y)
計算:=-9x²;+82xy-9y²;



若果16(x-y)²;-25=0 x與y的關係


16(x-y)²;-25=0
16(x-y)²;=25
(x-y)²;=25/16
x-y=±5/4



分解因式16(x+y)²;+40(x-y)²;+25(x-y)²;


錯了,中間是+40(x²;-y²;)
原式=[4(x+y)]²;+2[4(x+y)][5(x-y)]+[5(x-y)]²;
=[4(x+y)+5(x-y)]²;
=(9x-y)²;