Question

x+y=11
x*y=24
x²+y²=?

Answer 1

(x+y)^2=x^2+2xy+y^2=11^2=121

x^2+y^2=121-2*24=121-48=73

Answer 2

$(x+y)^{2} = x^{2} + y^{2} +2xy \\ 11^{2} = x^{2} + y^{2} +2*24 \\ x^{2} + y^{2} =121-48=73$