\(a,\left(x+3\right)\left(x+4\right)-\left(x-3\right)\left(x-5\right)=2\)
\(\Leftrightarrow x^2+3x+4x+12-\left(x^2-3x-5x+15\right)=2\)
\(\Leftrightarrow x^2+7x+12-\left(x^2-8x+15\right)=2\)
\(\Leftrightarrow x^2+7x+12-x^2+8x-15=2\)
\(\Leftrightarrow15x-3=2\)
\(\Leftrightarrow15x=5\Leftrightarrow x=\dfrac{1}{3}\)
\(b,x^2\left(x-3\right)-4x+12=0\)
\(\Leftrightarrow x^2\left(x-3\right)-4\left(x-3\right)=0\)
\(\Leftrightarrow\left(x-3\right)\left(x^2-4\right)=0\)
\(\Leftrightarrow\left(x-3\right)\left(x-2\right)\left(x+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-3=0\\x-2=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=3\\x=2\\x=-2\end{matrix}\right.\)
a) (x + 3)(x + 4) - (x - 3)(x - 5) = 2
x² + 4x + 3x + 12 - x² + 5x + 3x - 15 = 2
15x - 3 = 2
15x = 2 + 3
15x = 5
x = 5/15
x = 1/3
b) x²(x - 3) - 4x + 12 = 0
x²(x - 3) - 4(x - 3) = 0
(x - 3)(x² - 4) = 0
(x - 3)(x - 2)(x + 2) = 0
x - 3 = 0 hoặc x - 2 = 0 hoặc x + 2 = 0
*) x - 3 = 0
x = 0 + 3
x = 3
*) x - 2 = 0
x = 0 + 2
x = 2
*) x + 2 = 0
x = 0 - 2
x = -2
Vậy x = -2; x = 2; x = 3
