Tìm x biết:
(x+1)(3-2x)=-2x(x-5)
Tìm x biết: giúp với mn ơi
a) (x - 2)(x² + 2x+ 4) + x(x + 3)(3 - x) = 1
b) (2x + 1)³ - (2x - 1)³ - 6(2x - 1)² = 5
\(a,\Leftrightarrow x^3-8-x\left(x^2-9\right)=1\\ \Leftrightarrow x^3-8-x^3+9x=1\\ \Leftrightarrow9x=9\Leftrightarrow x=1\\ b,\Leftrightarrow8x^3+12x^2+6x+1-8x^3 +12x^2-6x+1-24x^2+24x-1=0\Leftrightarrow1=0\Leftrightarrow x\in\varnothing\)
a) \(\Leftrightarrow x^3-8-x^3+9x=1\)
\(\Leftrightarrow9x=9\Leftrightarrow x=1\)
b) \(\Leftrightarrow8x^3+12x^2+6x+1-8x^3+12x^2-6x+1-24x^2+24x-6=5\)
\(\Leftrightarrow24x=9\Leftrightarrow x=\dfrac{3}{8}\)
BT1: cho -3x(x+5)=-3x2-15x
(x+3)(x+2)=x2+5x+6
Tìm x biết:
--3x(x+5)+(x+3)(x+2)=7
BT2:Cho(2x+1)2=4x2+4x+1
(2x+1)(2x-1)=4x2-1
Tìm x biết:
(2x+1)2-(2x+1)(2x-1)=19
BT3: Tìm x biết:
a)x(x+1)-x(x+5)=9
b)4x2(x+5)-8x(x+7)=13
biết f(x)=x^2+2x+3/5 2x^3+3 ; g(x) = -2x^2-1/2x^3 -3x +6
tìm h(x) = 2f(x) - 1/2g(x)
tìm x biết a) 2x(x-1)-2x^2=-6 b) 2x(x-3)+5(x-3)=0
c) x^2+x-6=0
a: Ta có: \(2x\left(x-1\right)-2x^2=-6\)
\(\Leftrightarrow2x^2-2x-2x^2=-6\)
\(\Leftrightarrow x=3\)
b: Ta có: \(2x\left(x-3\right)+5\left(x-3\right)=0\)
\(\Leftrightarrow\left(x-3\right)\left(2x+5\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=3\\x=-\dfrac{5}{2}\end{matrix}\right.\)
Tìm x, biết
a)(2x-1)^5-(2x-1)^8=0
b)(2x+1). (2x-3)<0
c)(x-1). (2x+3)>0
,Tìm x, biết:
a, 3|x+4| - |2x+1| = 5
b, |x+5| - 3|2x+5| = 8
c,3|2x-3| - 6|x-1| = 3
Bài 1: Tìm x biết : 2x.(x+3)+(2x+3).(5-x)=2 Bài 2 : Tính x³+y³ biết x-y=4 và xy=5
Bài 1:
$2x(x+3)+(2x+3)(5-x)=2$
$\Leftrightarrow 2x^2+6x+(10x-2x^2+15-3x)=2$
$\Leftrightarrow 2x^2+6x+7x-2x^2+15=2$
$\Leftrightarrow 13x+15=2$
$\Leftrightarrow 13x=2-15=-13$
$\Leftrightarrow x=-13:13=-1$
Bài 2:
$x-y=4\Rightarrow x=y+4$. Thay vào $xy=5$ thì:
$(y+4)y=5$
$\Leftrightarrow y^2+4y-5=0$
$\Leftrightarrow (y-1)(y+5)=0$
$\Leftrightarrow y=1$ hoặc $y=-5$
Nếu $y=1$ thì $x=y+4=5$. Khi đó $x^3+y^3=5^3+1^3=126$
Nếu $y=-5$ thì $x=y+4=-1$. Khi đó: $x^3+y^3=(-1)^3+(-5)^3=-126$
Tìm x, biết:
a) |2x + 1| = 17
b) |3x − 17| = |2x − 3|
c) |x − 5| = 2x
d) |x − 1| + |x − 5| = 3
c) l x - 5 l = 2x
\(\Leftrightarrow\orbr{\begin{cases}x-5=2x\\x-5=-2x\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x-2x=5\\x+2x=5\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}-x=5\\3x=5\end{cases}}\)
\(\Leftrightarrow\orbr{\begin{cases}x=-5\\x=\frac{5}{3}\end{cases}}\)
Hok tốt!!!!!!!
Tìm x, biết:
a) |2x + 1| = 17
<=>\(\orbr{\begin{cases}2x+1=17\\2x+1=-17\end{cases}}\)
<=>\(\orbr{\begin{cases}2x=16\\2x=-18\end{cases}}\)
<=> \(\hept{\begin{cases}x=8\\x=-9\end{cases}}\)
Phần d không biết , thông cảm
a) Ta có :
| 2x + 1 | = 17
\(\Rightarrow\orbr{\begin{cases}2x+1=17\\2x+1=-17\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}2x=16\\2x=-18\end{cases}}\Rightarrow\orbr{\begin{cases}x=8\\x=-9\end{cases}}\)
b) | 3x - 17 | = | 2x - 3 |
Xét các trường hợp :
+) 3x - 17 = - 2x + 3
=> 3x + 2x = 3 + 17
=> 5x = 20
=> x = 4
+) 3x - 17 = 2x - 3
=> 3x - 2x = -3 + 17
=> x = 14
+) -3x + 17 = 2x - 3
=> 2x + 3x = 17 + 3x
=> 5x = 20
=> x = 4
c) | x - 5 | = 2x
\(\Rightarrow\orbr{\begin{cases}x-5=2x\\x-5=-2x\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}-x=5\\3x=5\end{cases}}\Rightarrow\orbr{\begin{cases}x=5\\x=\frac{5}{3}\end{cases}}\)
Tìm x biết:
a) 3(2x-1)(3x-3)-(2x-1)(3x-3)=-3
b) (3x-1)(2x+7)-(x+1)(6x-5)=x+2-(x+5)
Tìm x biết:
|x − 5| + |2x − 1| = 2x + 3.
TH1: \(x\ge5\)
<=> \(\left\{{}\begin{matrix}\left|x-5\right|=x-5\\\left|2x-1\right|=2x-1\end{matrix}\right.\)
PT <=> \(x-5+2x-1=2x+3\)
<=> x = 9 (Tm)
TH2: \(\dfrac{1}{2}\le x< 5\)
<=> \(\left\{{}\begin{matrix}\left|x-5\right|=5-x\\\left|2x-1\right|=2x-1\end{matrix}\right.\)
PT <=> 5 - x + 2x -1 = 2x + 3
<=> x = 1(Tm)
TH3: \(x< \dfrac{1}{2}\)
<=> \(\left\{{}\begin{matrix}\left|x-5\right|=5-x\\\left|2x-1\right|=1-2x\end{matrix}\right.\)
PT <=> \(5-x+1-2x=2x+3\)
<=> \(5x=3< =>x=\dfrac{3}{5}\left(l\right)\)
KL: x \(\in\left\{1;9\right\}\)