Question

Tìm x, biết:

a) (3x+4)² - (3x-1).(3x+1) =49

b) (2x+1)² - (x-1)² =0

Answer 1

a) (3x + 4)² - (3x - 1).(3x + 1) = 49

=> (3x + 4).3x + (3x + 4).4 - (9x² - 1) = 49

=> 9x² + 12x + 12x + 16 - 9x² + 1 = 49

=> 24x + 17 = 49

=> 24x = 49 - 17

=> 24x = 32

=> \(x=\frac{32}{24}=\frac{4}{3}\)

Vậy \(x=\frac{4}{3}\)

b) (2x + 1)² - (x - 1)² = 0

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

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

=> (x + 2).x = 0

\(\Rightarrow\left[\begin{array}{nghiempt}x+2=0\\x=0\end{array}\right.\) \(\Rightarrow\left[\begin{array}{nghiempt}x=-2\\x=0\end{array}\right.\)

Vậy \(\left[\begin{array}{nghiempt}x=-2\\x=0\end{array}\right.\)

Answer 2

a)

➜9x²+24x+16-9x²+1=49

➜24x +17=49

⇒24x=49

⇒x=4/3

b)⇒4x²+4x+1-x²+2x-1=0

⇒3x²+6x=0

⇒3x(x+3)=0

⇒3x=0 hoặc x+3 =0

⇒x=0 hoặc x=-3