Question

Sendo a
${a}^{2} + {b}^{2} = 24$
$( a+b)^{2} = 84$
Calcule:
$3ab$

Answer 1

Boa noite

a² + b² = 24
(a + b)² = 84 

a² + 2ab + b² = 84
2ab + 24 = 84
2ab = 84 - 24 = 60
ab = 60/2 = 30

3ab = 90