4, \(\dfrac{2}{x-2}+\dfrac{2x-12}{x^2-4}-\dfrac{3}{x+2}\)đk : x khác 2 ; -2
\(=\dfrac{2\left(x+2\right)+2x-12-3\left(x-2\right)}{\left(x-2\right)\left(x+2\right)}=\dfrac{2x+4+2x-12-3x+6}{\left(x-2\right)\left(x+2\right)}=\dfrac{1}{x+2}\)
Bài 2
a, \(2x+3xy=x\left(2+3y\right)\)
b, \(4x^2-25=\left(2x-5\right)\left(2x+5\right)\)
c, \(4x^2-4x+1-y^2=\left(2x-1\right)^2-y^2=\left(2x-1-y\right)\left(2x-1+y\right)\)
d, \(2a^3-16=2\left(a^3-8\right)=2\left(a-2\right)\left(a^2+2a+4\right)\)
Bài 3 :
1, (4x+1)(x+2)-4x(x-2)=19
<=> 4x^2 + 9x + 2 - 4x^2 + 8x = 19
<=> 17x = 17 <=> x = 1
2, x(x+5) = 6 <=> x^2 + 5x - 6 = 0
<=> x = 1 ; x = -6
