Question

Bài 2: (2 điểm) Tìm x, biết:

a)      (3x + 4)² – (3x – 1)(3x + 1) = 49

b)      x² – 4x + 4 = 9(x – 2)

c)      x² – 25 = 3x - 15

d)     (x – 1)³ + 3(x + 1)² = (x² – 2x + 4)(x + 2)

Answer 1

a) \(\Rightarrow9x^2+24x+16-9x^2+1=49\)

\(\Rightarrow24x=32\Rightarrow x=\dfrac{4}{3}\)

b) \(\Rightarrow x^2-13x+22=0\)

\(\Rightarrow\left(x-11\right)\left(x-2\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x=11\\x=2\end{matrix}\right.\)

c) \(\Rightarrow x^2-3x-10=0\)

\(\Rightarrow\left(x-5\right)\left(x+2\right)=0\)

\(\Rightarrow\left[{}\begin{matrix}x=5\\x=-2\end{matrix}\right.\)