Question

find the value of a^2+b^2 when a+b=5 and ab=6

Answer 1

a+b=5

ab=6

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

25=a^2+b^2+12

a^2+b^2=13

so your answer is 13

Answer 2

a^2+b^2= (a+b)^2 -2ab
5^2-2*6
25-12=13