Question

根据A-B=1,AB=6,你能求出A^2+B^2的值吗?A+B呢

Answer 1

(a-b)^2=1

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

a^2+b^2=1+2ab=1+2*6=13

(a+b)^2=a^2+b^2+2ab=13+6*2=25

a+b=5 or -5