Question

Tìm x biết 5x² - 2 = 9x

Answer 1

\(5x^2-9x-2=0\)

\(\Delta=9^2-4.5.\left(-2\right)=121\)

\(\left[{}\begin{matrix}x_1=\dfrac{9+\sqrt{121}}{2.5}=2\\x_2=\dfrac{9-\sqrt{121}}{2.5}=-\dfrac{1}{5}\end{matrix}\right.\)

Answer 2

\(5x^2-2=9x\)

\(5x^2=9x+2\)

\(5x^2=11x\)

\(=5.11x^3\)

= 55x³