Question

已知a-b=8,ab=12.求a+b的值

Answer 1

已知a-b=8,ab=12,

(a-b)^2=8^2

a^2-2ab+b^2=64

a^2-2ab+b^2+4ab=64+4ab

(a+b)^2=112

a+b=±4√ 7

已知a-b=2,ab=12,

(a-b)^2=2^2

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

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

(a+b)^2=52

a+b=±2√13

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

=1/2ab(a-2+b)

=1/2ab(a+b-2)

=1/2*12*(±2√13-2)

=±12√13- 12