4x^2-mxy+9y^2=(2x+3y)^2或(2x-3y)^2
(2x+3y)^2=4x^2+12xy+9y^2,故-m=12,m=-12
(2x-3y)^2=4x^2-12xy+9y^2,故得m=12
如果4x²-mxy+9y²是一个完全平方式,则m的值为多少?
4x^2-mxy+9y^2=(2x+3y)^2或(2x-3y)^2
(2x+3y)^2=4x^2+12xy+9y^2,故-m=12,m=-12
(2x-3y)^2=4x^2-12xy+9y^2,故得m=12