x的平方+7.5X=28 X等于多少啊?
问题描述：
x的平方+7.5X=28 X等于多少啊?
答
x^2+7.5x=28
x^2+2*3.75x+3.75^2=28+3.75^2=42.0625
(x+3.75)^2=42.0625
x+3.75=±√42.0625
x=-3.75±√42.0625