Question

Tìm x, biết:

-7x (x² - 6x - 6) = -7x³ + x

Answer 1

\(\Leftrightarrow-7x^3+42x^2+42x=-7x^3+x\)

\(\Leftrightarrow42x^2+41x=0\)

\(\Leftrightarrow x\left(42x+41\right)=0\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\42x+41=0\end{matrix}\right.\)

\(\Leftrightarrow\left[{}\begin{matrix}x=0\\x=-\dfrac{41}{42}\end{matrix}\right.\)

Answer 2

- 7x (x² - 6x - 6) = - 7x³ + x

<=> - 7x³ + 42x² + 42x = - 7x³ + x

<=> 42x² + 41x = 0

<=> x (42x + 41) = 0

<=> [ x = 0 <=> [42x + 41 = 0

<=> [ x = 0 <=> [ x = - 41/42