Question

已知a+b的平方等于7,a-b的平方等于4,求a平方加b平方和ab的值.

Answer 1

2(a^2+b^2)

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

=7-4

=3

a^2+b^2

=3÷2

=1.5

2ab

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

=7-1.5

=5.5

ab

=5.5÷2

=11/4