Question

Tìm x biết

A, 3x^2+8x+4=0

B, 4x^2-4x-3=0

 

Answer 1

a) 3x² + 8x + 4 = 0

=> 3x² + 6x + 2x +  4 = 0

=> 3x(x + 2) + 2(x + 2) = 0

=> (3x + 2)(x + 2) = 0

=> \(\orbr{\begin{cases}3x+2=0\\x+2=0\end{cases}}\)

=> \(\orbr{\begin{cases}x=-\frac{2}{3}\\x=-1\end{cases}}\)

b) 4x² - 4x - 3 = 0

=> 4x² - 6x + 2x - 3 = 0

=> 2x(2x - 3) + (2x - 3) = 0

=> (2x + 1)(2x - 3) = 0

=> \(\orbr{\begin{cases}2x+1=0\\2x-3=0\end{cases}}\)

=> \(\orbr{\begin{cases}x=-\frac{1}{2}\\x=\frac{3}{2}\end{cases}}\)

Answer 2

\(a,3x^2+8x+4=0\) 

\(\Rightarrow3x^2+6x+2x+4=0\) 

\(\Rightarrow3x\left(x+2\right)+2\left(x+2\right)=0\) 

\(\Rightarrow\left(3x+2\right)\left(x+2\right)=0\)

\(\Rightarrow\orbr{\begin{cases}3x+2=0\\x+2=0\end{cases}\Rightarrow\orbr{\begin{cases}x=\frac{-2}{3}\\x=-2\end{cases}}}\)

Vậy....