Giải pt sau: 4x^2 – 9 = (x – 7) (2x – 3) 02/11/2021 Bởi Remi Giải pt sau: 4x^2 – 9 = (x – 7) (2x – 3)
$4x^2-9=(x-7)(2x-3)$$↔4x^2-9=2x^2-3x-14x+21$$↔4x^2-9-2x^2+3x+14x-21=0$$↔2x^2+17x-30=0$$↔2x^2+20x-3x-30=0$$↔2x(x+10)-3(x+10)=0$$↔(x+10)(2x-3)=0$$↔\left[\begin{array}{l}x+10=0\\2x-3=0\end{array}\right.↔\left[\begin{array}{l}x=-10\\x=\dfrac32\end{array}\right.$ Vậy `S={-10;3/2}` Bình luận
$4x^2-9=(x-7)(2x-3)$
$↔4x^2-9=2x^2-3x-14x+21$
$↔4x^2-9-2x^2+3x+14x-21=0$
$↔2x^2+17x-30=0$
$↔2x^2+20x-3x-30=0$
$↔2x(x+10)-3(x+10)=0$
$↔(x+10)(2x-3)=0$
$↔\left[\begin{array}{l}x+10=0\\2x-3=0\end{array}\right.↔\left[\begin{array}{l}x=-10\\x=\dfrac32\end{array}\right.$
Vậy `S={-10;3/2}`