tìm x biết:
a)2x(x-5)-x(3+2x)=26
b)5x(1-2x)-3x(x+18)=0
c)5x-3{4x-2[4x-3(5x-2)]}=182
d)(x+2)(x+3)-(x-2)(x+5)=0
e)(8x-3)(3x+2)-(4x+7)(x+4)=(2x+1)(5x-1)-33
tìm x biết:
a)2x(x-5)-x(3+2x)=26
b)5x(1-2x)-3x(x+18)=0
c)5x-3{4x-2[4x-3(5x-2)]}=182
d)(x+2)(x+3)-(x-2)(x+5)=0
e)(8x-3)(3x+2)-(4x+7)(x+4)=(2x+1)(5x-1)-33
Đáp án:
a)=>2x²-10x-3x-2x²=26
=>-13x=26
=>x=-2
b)=>5x-10x²-3x²-54x=0
=>-13x²-49x=0
=>-x(13x+49)=0
=>x=0
hoặc x=-49/13
Đáp án:
$a) 2x(x-5) -x(3+2x)=26$
$⇔ 2x^2-10x -3x-2x^2 =26$
$⇔ -13x=26$
$⇔x = 26 : (-13)$
$⇔x = -2 $
Vậy $x=-2$
$b) 5x(1-2x) -3x(x+18) =0$
$⇔ 5x-10x^2-3x^2-54x = 0$
$⇔ -13x^2-49x=0$
$⇔x(-13x-49)=0$
⇔\(\left[ \begin{array}{l}x=0\\-13x-49=0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=0\\x=-\dfrac{49}{13}\end{array} \right.\)
Vậy $\text{ x ∈ { $ 0 ; -\dfrac{49}{13}$ }}$
$c) 5x-3{4x-2) [4x-3(5x-2)]} = 182$
$⇔ 5x-3{4x-2[4x-15x+6]} = 182$
$⇔ 5x -3{4x-8x+30x-12} =182$
$⇔ 5x -12x+24x-90x+36 = 182$
$⇔ 5x-12x+24x-90x = 182-36$
$⇔-73x = 146$
$⇔ x = 146 : (-73)$
$⇔x= -2$
Vậy $x=-2$
$d) (x+2)(x+3) -(x-2)(x+5)=0$
$⇔x^2+3x+2x+6 -x^2-5x+2x+10 =0$
$⇔ 2x +16=0$
$⇔ 2x = -16$
$⇔x=-16 : 2$
$⇔ x = -8$
Vậy $x=-8$
$e) (8x-3)(3x+2) -(4x+7)(x+4) =(2x+1)(5x-1) -33$
$⇔ 24x^2+16x-9x-6 -4x^2-16x-7x-28 = 10x^2-2x+5x-1 -33$
$⇔ 24x^2-4x^2-10x^2 +16x-9x-16x-7x+2x-5x-6-28+1+33=0$
$⇔10x^2-19x=0$
$⇔x(10x-19)=0$
⇔\(\left[ \begin{array}{l}x=0\\10x-19=0\end{array} \right.\)
⇔\(\left[ \begin{array}{l}x=0\\x=\dfrac{19}{10}\end{array} \right.\)
Vậy $\text{ x ∈ { $0 ; \dfrac{19}{10}$}}$