x^2-y^2=(x+4)(7-y),则x^y-2=

问题描述:

x^2-y^2=(x+4)(7-y),则x^y-2=

x^2-y^2
=(x+y)(x-y)=(x+4)(7-y)所以y=4 x=7于是x^y-2=7^2=49