Tìm x, biết
a)\(\left|x+1\right|\) +2x=-2
b)x^2-6x+9=1
TÌM X, BIẾT
\(\left(3x+2\right)\left(2x+9\right)-\left(x+2\right)\left(6x+1\right)=\left(x+1\right)-\left(x-6\right)\)
\(\Leftrightarrow6x^2+4x+27x+18-6x^2-12x-x-2=x^2-x-6x-6\)
\(\Leftrightarrow18x+16=x^2-7x-6\)
\(\Leftrightarrow x^2-7x-18x=16+6\)
\(\Leftrightarrow x^2-15x=22\)
\(\Leftrightarrow x^2-15x-22=0\)
......
Tìm x biết:
\(\left(3x+2\right)\left(2x+9\right)-\left(x+2\right)\left(6x+1\right)=\left(x-1\right)-\left(x-6\right)\)
\(\Leftrightarrow\left(6x^2+27x+4x+18\right)-\left(6x^2+x+12x+2\right)=x-1-x+6\)
\(\Leftrightarrow6x^2+31x+18-6x^2-x-12x-2=7\)
\(\Leftrightarrow18x+16=7\)
\(\Leftrightarrow18x=-9\)
\(\Leftrightarrow x=\frac{-1}{2}\)
\(\left(3x+2\right)\left(2x+9\right)-\left(x+2\right)\left(6x+1\right)=\left(x-1\right)-\left(x-6\right)\)
\(3x\left(2x+9\right)+2\left(2x+9\right)-x\left(6x+1\right)-2\left(6x+1\right)=x-1-x+6\)
\(6x^2+27x+4x+18-6x^2-x-12x-2=5\)
\(6x^2+\left(27x+4x\right)+18-6x^2-\left(12x+x\right)-2=5\)
\(6x^2+31x+18-6x^2-13x-2=5\)
\(\left(6x^2-6x^2\right)+\left(31x-13x\right)+\left(18-2\right)=5\)
\(18x+16=5\)
\(18x=5+16\)
\(18x=21\)
\(x=21:18\)
\(x=\frac{7}{6}\)
Vậy \(x=\frac{7}{6}\)
P/s: Mình mới lớp 6 nên hi vọng bn xem bài của mik thật kĩ xem có sai sót không,cảm ơn.
Tìm x, biết
a)\(\left|x+1\right|\) +2x=-2
b)x^2-6x+9=1
a, |x+1| +2x \(=\)-2
\(\Leftrightarrow\) |x+1|\(=\)-2-2x (*)
TH1: Nếu x+1\(\ge0\)\(\Leftrightarrow x\ge-1\)thì \(\left|x+1\right|=x+1\)
Thay vào (*) ta có:
\(x+1=-2-2x\)
\(\Leftrightarrow x+2x=-2-1\)
\(\Leftrightarrow3x=-3\)
\(\Leftrightarrow x=-1\)(TMĐK)
TH2: Nếu \(x+1< 0\Leftrightarrow x< -1\Rightarrow\left|x+1\right|=-\left(x+1\right)\)
Thay vào (*), ta có:
\(-x-1=\)\(-2-2x\)
\(\Leftrightarrow-x+2x=-2+1\)
\(\Leftrightarrow x=-1\)(kTMĐK)
Vậy S\(=\){-1}
b, \(x^2-6x+9=1\)
\(\Leftrightarrow x^2-2.3.x+3^2\)
\(\Leftrightarrow\left(x-3\right)^2=1\)
\(\Leftrightarrow\left(x-3\right)^2-1^2=0\)
\(\Leftrightarrow\left(x-3-1\right)\left(x-3+1\right)=0\)
\(\Leftrightarrow\left(x-4\right)\left(x-2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x-4=0\\x-2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=4\\x=2\end{matrix}\right.\)
Vậy S\(=\){4;2}
a) |x + 1| + 2x = 2
\(\Rightarrow\) |3x + 1| = 2
\(\Rightarrow\) |3x| = 1
\(\Rightarrow\) |x| = 1 : 3 = \(\dfrac{1}{3}\)
\(\Rightarrow\) x = \(\dfrac{1}{3}\) hoặc \(-\dfrac{1}{3}\)
Tìm x biết
a) \(\left|x+1\right|\) +2x=-2
b) x^2-6x+9=1
a: \(\Leftrightarrow\left|x+1\right|=-2x-2\)
\(\Leftrightarrow\left[{}\begin{matrix}\left(-2x-2\right)^2-\left(x+1\right)^2=0\\-2x-2>=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}3\left(x+1\right)^2=0\\x< =-1\end{matrix}\right.\Leftrightarrow x=-1\)
b: \(\Leftrightarrow\left(x-3\right)^2=1\)
\(\Leftrightarrow\left[{}\begin{matrix}x-3=1\\x-3=-1\end{matrix}\right.\Leftrightarrow x\in\left\{4;2\right\}\)
Tìm x, biết
a) \(\left(3x+2\right)\left(2x+9\right)-\left(x+2\right)\left(6x+1\right)=\left(x+1\right)-\left(x-6\right)\)
b) \(3\left(2x-1\right)\left(3x-1\right)-\left(2x-3\right)\left(9x-1\right)=0\)
a) (3x+2)(2x+9) - (x+2)(6x+1) = (x+1) - (x-6)
<=> 6x2 + 27x + 4x + 18 - 6x2 - x - 12x - 2 = x+1 - x+6
<=> 18x + 16 = 7
<=> 18x = -9
<=> x = \(-\dfrac{1}{2}\)
b) 3(2x-1)(3x-1) - (2x-3)(9x-1) = 0
<=> 3.(6x2-2x-3x+1) - (18x2-2x-27x+3) = 0
<=> 3.(6x2-5x+1) - 18x2+29x-3 = 0
<=> 18x2-15x+3 - 18x2+29x - 3 = 0
<=> 14x = 0
<=> x = 0
Tìm x biết :
\(x^2-6x+9=\left(2x+1\right)^2\)
\(x^2-6x+9=\left(2x+1\right)^2\)
\(\Rightarrow\left(x-3\right)^2=\left(2x+1\right)^2\)
\(\Rightarrow\left(x-3\right)^2-\left(2x+1\right)^2=0\)
\(\Rightarrow\left(x-3-2x-1\right)\left(x-3+2x+1\right)=0\)
\(\Rightarrow-\left(x+4\right)\left(3x-2\right)=0\)
\(\Rightarrow\left[\begin{array}{nghiempt}x+4=0\\3x-2=0\end{array}\right.\)
\(\Rightarrow\left[\begin{array}{nghiempt}x=-4\\x=\frac{2}{3}\end{array}\right.\)
Vậy x = -4 ; \(\frac{2}{3}\)
x² + 6x + 9 = (2x-1) ²
sử dụng công thức nhân tóm tắt (ab) ² = a²-2ab + b² và chúng tôi mang lại phương trình để các hình thức:
x² + 6x + 9 = 4x²-4x + 1
đặt phương trình:
-3x² + 10x + 8 = 0
đã nhận được bình đẳng vuông, mà bây giờ được giải quyết:
-3x² + 10x + 8 = 0
Δ = b²-4ac = 100- (4 * (- 3) * 8) = 100 - (- 96) = 100 + 96 = 196
√Δ = 14
x₁ = (- b-√Δ): 2a = (- 10-14): (- 6) = (- 24): (- 6) = 4
x₂ = (- b + √Δ): 2a = (- 10 + 14) (- 6) = 4 (- 6) = -4/6 = -2/3
x∈ {-2/3; 4}
Tìm x biết:
\(\left(3x+2\right)\left(2x+9\right)-\left(x+2\right)\left(6x+1\right)=\left(x-1\right)-\left(x-6\right)\)
Giải:
\(\left(3x+2\right)\left(2x+9\right)-\left(x+2\right)\left(6x+1\right)=\left(x-1\right)-\left(x-6\right)\)
\(\Leftrightarrow6x^2+4x+27x+18-\left(6x^2+12x+x+2\right)=x-1-x+6\)
\(\Leftrightarrow6x^2+4x+27x+18-6x^2-12x-x-2=5\)
\(\Leftrightarrow16+18x=5\)
\(\Leftrightarrow18x=-11\)
\(\Leftrightarrow x=-\dfrac{11}{18}\)
Vậy ...
tìm x biết
a)\(\left(x-2\right)^2-x\left(x+1\right)\left(x-1\right)+6x\left(x-3\right)=0\)
b)\(\left(x-2\right)\left(x^2-2x+4\right)\left(x+2\right)\left(x^2+2x+4\right)-x^6+2x=1\)
c)\(\left(x-3\right)\left(x^2+3x+9\right)+x\left(x+2\right)\left(2-x\right)=1\)
b) Ta có: \(\left(x-2\right)\left(x^2-2x+4\right)\left(x+2\right)\left(x^2+2x+4\right)-x^6+2x=1\)
\(\Leftrightarrow\left(x^3-8\right)\left(x^3+8\right)-x^6+2x-1=0\)
\(\Leftrightarrow x^6-64-x^6+2x-1=0\)
\(\Leftrightarrow2x-65=0\)
\(\Leftrightarrow2x=65\)
hay \(x=\frac{65}{2}\)
Vậy: \(x=\frac{65}{2}\)
c) Ta có: \(\left(x-3\right)\left(x^2+3x+9\right)+x\left(x+2\right)\left(2-x\right)=1\)
\(\Leftrightarrow x^3-27-x\left(x+2\right)\left(x-2\right)-1=0\)
\(\Leftrightarrow x^3-27-x\left(x^2-4\right)-1=0\)
\(\Leftrightarrow x^3-27-x^3+4x-1=0\)
\(\Leftrightarrow4x-28=0\)
\(\Leftrightarrow4x=28\)
hay x=7
Vậy: x=7
Tìm giá trị của k sao cho phương trình
a) \(\left(2x+1\right)^2\)(9x+2k) - 5(x+2)=40 có nghiệm là x=2
b) 2(2x-1)+18=9(x+2)(2x+k) có nghiệm là x=1
a) Để phương trình \(\left(2x+1\right)^2\cdot\left(9x+2k\right)-5\left(x+2\right)=40\) có nghiệm là x=2 thì Thay x=2 vào phương trình \(\left(2x+1\right)^2\cdot\left(9x+2k\right)-5\left(x+2\right)=40\), ta được:
\(\left(2\cdot2+1\right)^2\cdot\left(9\cdot2+2k\right)-5\left(2+2\right)=40\)
\(\Leftrightarrow25\cdot\left(2k+18\right)-20=40\)
\(\Leftrightarrow25\left(2k+18\right)=60\)
\(\Leftrightarrow2k+18=\dfrac{12}{5}\)
\(\Leftrightarrow2k=-\dfrac{78}{5}\)
hay \(k=\dfrac{-39}{5}\)
Vậy: \(k=\dfrac{-39}{5}\)
(9x+2k) - 5(x+2)=40 có nghiệm là x=2
=>(2*2+1)2(9*2+2k)-5(2+2)=40
=>25(18+5k)-20=40
=>25(18+5k)=60
=>18+5k=2.4
=>5k=-15.6 =>k=-0.624
b) 2(2x-1)+18=9(x+2)(2x+k) có nghiệm là x=1
=>2(2*1-1)+18=9(1+2)(2*1+k)
=>2+18=27(2+k)
=>2+k=20/27
=>k=-34/27