已知9x^2-12xy+4y^2+30x-20y+25=0,求9x^2-12xy+4y^2的值
问题描述:
已知9x^2-12xy+4y^2+30x-20y+25=0,求9x^2-12xy+4y^2的值
答
已知9x^2-12xy+4y^2+30x-20y+25=0,
(3x-2y)^2+10(3x-2y)+5^2=0
(3x-2y+5)^2=0
3x-2y=-5
(3x-2y)^2=25
9x^2-12xy+4y^2=(3x-2y)^2=25