Question

Si a^2 +b^2 =20 y (a+b)^2=36 calcular ab

Answer 1

a² + b² = 20

( a+b )² = 36

a² + 2ab + b² = 36

a² + b² + 2ab = 36

  20   +  2ab  = 36

            2ab = 36 - 20

            2ab = 16

              ab = 16/2

              ab = 8

Answer 2

$a^{2}+b^{2} = 20\\\\\\a^{2}+2ab+b^{2}\\a^{2}+b^{2}+2ab\\20 +2ab =36\\2ab=16\\ab=8$