Question

tìm x, biết :

a) (x - 2)²  -(x + 3)² -4( x + 1) =5

Answer 1

\(\left(x-2\right)^2-\left(x+3\right)^2-4\left(x+1\right)=5\Rightarrow x^2-4x+4-x^2-6x-9-4x-4=5\Rightarrow-14x=14\Rightarrow x=-1\)

Answer 2

\(\Rightarrow\left[\left(x-2\right)^2-\left(x+3\right)^2\right]-4\left(x+1\right)\)=5

\(\Rightarrow\left(x-2-x-3\right)\left(x-2+x+3\right)-4x-4=5\)

\(\Rightarrow-5.\left(2x+1\right)-4x-4=5\)

\(\Rightarrow-10x-5-4x-4=5\)

\(\Rightarrow-14x-9=5\Rightarrow-14x=14\Rightarrow x=-1\)

Answer 3

\(\Leftrightarrow\) x²-2.x.2+2² - (x²+2.x.3+3²)- 4x-4=5

\(\Leftrightarrow\) x²-4x+4-x²-6x-9-4x-4-5=0

\(\Leftrightarrow\) -14x-14=0

\(\Leftrightarrow\)-14x =14

\(\Leftrightarrow\) x=-1

 

Answer 4

Ta có: \(\left(x-2\right)^2-\left(x+3\right)^2-4\left(x+1\right)=5\)

\(\Leftrightarrow x^2-4x+4-x^2-6x-9-4x-4=5\)

\(\Leftrightarrow-14x=10\)

hay \(x=-\dfrac{5}{7}\)