Question

-4x²(x-7)+4x(x²-5)=28x²-13

Answer 1

\(\Leftrightarrow-4x^3+28x^2+4x^3-20x-28x^2+13=0\\ \Leftrightarrow\left(-4x^3+4x^3\right)+\left(28x^2-28x^2\right)-20x+13=0\\ \Leftrightarrow-20x=-13\\ \Leftrightarrow x=\dfrac{13}{20}\)

Vậy \(x=\dfrac{13}{20}\)