84x(x+2) = 84x² + 168x
84x² + 168x = 90 - 13x
84x² +181x - 90 = 0
bhaskara formula
[tex]\frac{-181+-\sqrt{181^{2}- 4.84.(-90) } }{168 } }[/tex]
[tex]\frac{-181+-\sqrt{32.761 +30.240} }{168}[/tex]
[tex]\frac{-181+-251}{168}[/tex]
since its a positive number, we can't use the minus
so, [tex]\frac{70}{168}[/tex]
they're both dividable by 14, so
x = [tex]\frac{5}{12}[/tex] is your answer
hope it helps :)
