Question

Find all pairs ( a, b ) such that 2a + b = 12 and ab = 3.

Answer 1

a=3/b (b is not 0)
so
2a+b=12 is the same as
2(3/b)+b = 12
6/b+b=12

6+b^2=12
b^2=6
b = sqrt(6)
so b = 3/sqrt(6)

Answer 2

+- sqrt(6)