Question

若a^2+ab=4,ab+b^2=-1,则a^2+2ab+b^2= ,a^2-b^2= .

Answer 1

若a^2+ab=4,ab+b^2=-1,

两个式子相加得

a^2+2ab+b^2=4-1=3

两个式子相减得

a^2-b^2=4-（-1）=5