已知x^2+xy=13,且xy+y2=12,求(x+y)(x-y)和（x+y）^2_数学解答

已知x^2+xy=13,且xy+y2=12,求(x+y)(x-y)和（x+y）^2

人气：262 ℃　时间：2020-07-01 11:16:08

解答

x^2+xy=13,且xy+y2=12
∴(x+y)(x-y)
=x²-y²
=x²+xy-xy-y²
=x²+xy-(xy+y²)
=13-12
=1
(x+y)²=x²+2xy+y²
=x²+xy+xy+y²
=13+12
=25