Hello, please consider the following.
[tex]\begin{aligned}5(9x^2+9x+10) &= x(9x-40)\\&=9x^2-40x\end{aligned}\\\\<=> 45x^2+45x+50=9x^2-40x\\\\<=> (45-9)x^2+(45+40)x+50=0\\\\<=> 36x^2+85x+50=0[/tex]
We can estimate the discriminant, and then, the solutions and we take the largest one.
[tex]\Delta=b^2-4ac=85^2-4*36*50=25=5^2\\\\x_1=\dfrac{-85-5}{2*36}=\dfrac{-18*5}{18*4}=\dfrac{-5}{4}\\\\x_2=\dfrac{-85+5}{2*36}=\dfrac{-80}{72}=\dfrac{-8*10}{8*9}=\boxed{\dfrac{-10}{9}}[/tex]
Thank you
