Question

tìm x biết: (2x-3)² ​-4(x-1)(x+1)=49

Answer 1

Ta có: (2x)² -2.2x.3 +3² - 4.(x² - 1²) = 49

⇒4x² - 12x + 9 - 4x² + 4 = 49

⇒-12x = 49 - 9 - 4

⇒-12x = 36

⇒x = -3

Answer 2

\(\left(2x-3\right)^2-4\left(x-1\right)\left(x+1\right)=49\)
\(\Leftrightarrow\left[\left(2x\right)^2-2.2x.3+3^2\right]-4\left(x^2-1^2\right)=49\)
\(\Leftrightarrow4x^2-12x+9-4x^2+4=49\)
\(\Leftrightarrow-12x+13=49\)
\(\Leftrightarrow-12x=36\)
\(\Leftrightarrow x=-3\)
\(\text{Vậy }x=-3\)

Answer 3

\(\left(2x-3\right)^2-4\left(x-1\right)\left(x+1\right)=49\)

\(\Leftrightarrow4x^2-12x+9-4\left(x^2-1\right)=49\)

\(\Leftrightarrow4x^2-12x+9-4x^2+4=49\)

\(\Leftrightarrow-12x=49-9-4=36\)

\(\Leftrightarrow x-3\)

Answer 4

\(\left(2x-3\right)^2-4\left(x-1\right)\left(x+1\right)=49\)

\(\Leftrightarrow4x^2-12x+9-4\left(x^2-1\right)=49\)

\(\Leftrightarrow4x^2-12x+9-4x^2+4=49\)

\(\Leftrightarrow12x+9+4=49\)

\(\Leftrightarrow12x=36\)

\(\Leftrightarrow x=3\)