Question

sendo (a+b)² = 81  e a²+b²  = 53 calcule o valor de 3ab 

Answer 1

$(a+b)^2=a^2+b^2+2ab\rightarrow 53+2ab=81 \\ \\ 2ab=81-53=28 \\ \\ ab=\frac{28}{2}=14 \\ \\ \boxed{3ab=3.14=42}$