Question

已知a的平方+b的平方-4a+6b+13=0,求a+b的值.

Answer 1

a^2+b^2-4a+6b+13=0

(a-2)^2+(b+3)^2=0

a=2,b=-3

a+b=-1

a=-b

(a+4)^2-(b+4)^2=16

(a+4-b-4)(a+4+b+4)=-2b*8=16,b=-1

a=1

4a^2-b=4+1=5

(133+3/7)^2+(86+4/7)^2+2*(133+3/7)(86+4/7)

=(133+3/7+86+4/7)^2

=(133+87)^2

=220^2

=48400