Question

Sabendo que 5x+3y = 18, e que 5x²y+3xy² = 90, podemos dizer que o valor
de 7xy é:

a) 150
b) 5
c) 35
d) 1620

Answer 1

$\boxed{\begin{array}{l}\sf 5x+3y=18\\\sf 5x^2y+3xy^2=90\\\sf xy(5x+3y)=90\\\sf xy\cdot18=90\\\sf xy=\dfrac{90}{18}\\\\\sf xy=5\\\sf 7xy=7\cdot5=35\\\huge\boxed{\boxed{\boxed{\boxed{\sf\maltese~alternativa~c}}}} \end{array}}$