Question

Tìm x, biết:

a, 4x² + 4x + 1 = 25

b, x³ - 3x² + 3x - 2 = 0

c, 7x³ - 3x² - 3x - 1 = 0

Answer 1

a, 4x² + 4x + 1 = 25

⇔ ( 2x + 1 ) \(^2\) - 25 = 0

⇔( 2x + 1 - 5 ) ( 2x + 1 + 5 ) =0

⇔ ( 2x - 4 ) ( 2x + 6 ) = 0

\(\Leftrightarrow\left[{}\begin{matrix}2x-4=0\\2x+6=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\x=-3\end{matrix}\right.\)

Answer 2

a) 4x² + 4x +1 = 25

⇌ ( 2x+ 1)² - 25 = 0

( 2x + 1 - 5) (2x + 1 + 5) = 0

(2x - 4) (2x + 6) = 0

\(⇌\left[{}\begin{matrix}2x-4=0\\\\2x+6=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=2\\\\x=-3\end{matrix}\right.\)

Hk tốt!