Question

a+b=4
a x b = 2
a^2 + b^2 =?

Answer 1

$a + b = 4 \: \: \: | ^{2} \\ \\ {(a + b)}^{2} = {4}^{2} \\ \\ {a}^{2} + 2ab + {b}^{2} = 16 \\ \\ {a}^{2} + {b}^{2} = 16 - 2 \times 2 = 16 - 4 = 12$

Answer 2

$(a+b)^{2}$=$a^{2}$+$b^{2}$+2ab

$(a+b)^{2}$=$4^{2}$=16

$a^{2}$+$b^{2}$=16-2ab=16-2*2=16-4=12