Question 397724
We have {{{ab = 10}}} and {{{a^2 + b^2 = 30}}}. Since


{{{(a+b)^2 = a^2 + 2ab + b^2 = a^2 + b^2 + 2ab}}}, we can substitute {{{a^2 + b^2}}} and {{{ab}}} to obtain


{{{(a+b)^2 = 30 + 2(10) = 50}}} so choice C is correct.