Question

Tìm x, biết:

1, \(\left(x-4\right)^{^2}-\left(x-2\right)\left(x+2\right)=6\)

1, \(9\left(x+1\right)^2-\left(3x-2\right)\left(3x+2\right)=10\)

Answer 1

1: x² - 8x +16 -x²+4=6

-8x + 20 =6

-8x = -14

x = 7/4

Answer 2

a) \(\left(x-4\right)^2-\left(x-2\right)\left(x+2\right)=0\)

\(\Leftrightarrow x^2-8x+16-x^2+4=0\)

\(\Leftrightarrow20-8x=0\)

\(\Leftrightarrow8x=20\)

\(\Leftrightarrow x=\dfrac{5}{2}\)

Vậy x = \(\dfrac{5}{2}\)

b) \(9\left(x+1\right)^2-\left(3x-2\right)\left(3x+2\right)=10\)

\(\Leftrightarrow9\left(x^2+2x+1\right)-9x^2+4-10=0\)

\(\Leftrightarrow9x^2+18x+9-9x^2+4-10=0\)

\(\Leftrightarrow18x+3=0\)

\(\Leftrightarrow18x=-3\)

\(\Leftrightarrow x=\dfrac{-1}{6}\)

Vậy x = \(\dfrac{-1}{6}\)