104. Giải các phương trình:
a) \(2x^3-x^2-8x+4=0\)
b) \(3x^3+6x^2-75x-150=0\)
c) \(2x^5-3x^4+6x^3-8x^2+3=0\)
Giải phương trình
a, (x^2-2)(x^2+x+1)=0
b, 16x^2 - 8x + 5=0
c, 2x^3 - x^2 - 8x + 4=0
d, 3x^3+6x^2 - 75x -150 = 0
e, 2x^5-3x^4+6x^3-8x^2+3=0
*vn:vô nghiệm.
a. \(\left(x^2-2\right)\left(x^2+x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x^2-2=0\\x^2+x+1=0\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}\left(x-\sqrt{2}\right)\left(x+\sqrt{2}\right)=0\\\left(x+\dfrac{1}{2}\right)^2+\dfrac{3}{4}=0\left(vn\right)\end{matrix}\right.\)
\(\Leftrightarrow x=\pm\sqrt{2}\)
-Vậy \(S=\left\{\pm\sqrt{2}\right\}\).
b. \(16x^2-8x+5=0\)
\(\Leftrightarrow16x^2-8x+1+4=0\)
\(\Leftrightarrow\left(4x-1\right)^2+4=0\) (vô lí)
-Vậy S=∅.
c. \(2x^3-x^2-8x+4=0\)
\(\Leftrightarrow x^2\left(2x-1\right)-4\left(2x-1\right)=0\)
\(\Leftrightarrow\left(2x-1\right)\left(x^2-4\right)=0\)
\(\Leftrightarrow\left(2x-1\right)\left(x-2\right)\left(x+2\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=\dfrac{1}{2}\\x=\pm2\end{matrix}\right.\)
-Vậy \(S=\left\{\dfrac{1}{2};\pm2\right\}\).
d. \(3x^3+6x^2-75x-150=0\)
\(\Leftrightarrow3x^2\left(x+2\right)-75\left(x+2\right)=0\)
\(\Leftrightarrow3\left(x+2\right)\left(x^2-25\right)=0\)
\(\Leftrightarrow3\left(x+2\right)\left(x+5\right)\left(x-5\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=\pm5\end{matrix}\right.\)
-Vậy \(S=\left\{-2;\pm5\right\}\)
Bài1:Giải phương trình:
a,(5-x)(3-2x)(3x+4)=0
b,(2x-1)(3x+2)(5-x)=0
c,(2x-1)(x-3)(x+7)=0
Giúp mình với :)
d,(3-2x)(6x+4)(5-8x)=0
a,\(x\in\left\{5;1,5;\dfrac{-4}{3}\right\}\)
Giải các phương trình sau:
a \(x^4=5x^2+2x-3\)
b \(x^4=6x^2+12x+10\)
c \(3x^3+3x^2+3x=-1\)
d \(8x^3-12x^2+6x-5=0\)
Giải các phương trình sau:
a \(x^2+3x+4=0\)
b \(3x^3-x+2=0\)
c \(x^4-4x^3-9x^2+8x+4=0\)
d \(x^4+4x^3+6x^2-5x-8=0\)
a: Ta có: \(x^2+3x+4=0\)
\(\text{Δ}=3^2-4\cdot1\cdot4=9-16=-7< 0\)
Do đó: Phương trình vô nghiệm
tìm x biết
a/x^3+3x^2+3x+2=0
b/x^4-2x^3+2x-1=0
c/x^4-3x^3-6x^2+8x=0
a) \(x^3+3x^2+3x+2=0\)
<=> \(x^3+x^2+x+2x^2+2x+2=0\)
<=> \(x\left(x^2+x+1\right)+2\left(x^2+x+1\right)=0\)
<=> \(\left(x+2\right)\left(x^2+x+1\right)=0\)
tự làm
b) \(x^4-2x^3+2x-1=0\)
<=> \(\left(x^4-3x^3+3x^2-x\right)+\left(x^3-3x^2+3x-1\right)=0\)
<=> \(x\left(x^3-3x^2+3x-1\right)+\left(x^3-3x^2+3x-1\right)=0\)
<=> \(\left(x^3-3x^2+3x-1\right)\left(x+1\right)=0\)
<=> \(\left(x-1\right)^3\left(x+1\right)=0\)
tự làm
c) \(x^4-3x^3-6x^2+8x=0\)
<=> \(x\left(x^3-3x^2-6x+8\right)=0\)
<=> \(x\left[\left(x^3+x^2-2x\right)-\left(4x^2+4x-8\right)\right]=0\)
<=>\(x\left[x\left(x^2+x-2\right)-4\left(x^2+x-2\right)\right]=0\)
<=> \(x\left(x-4\right)\left(x^2+x-2\right)=0\)
<=> \(x\left(x-4\right)\left(x-1\right)\left(x+2\right)=0\)
tự làm
Giải phương trình tích
7)(16-8x)(2-6x)=0
8) (x+4)(6x-12)=0
9) (11-33x)(x+11)=0
10) (x-1/4)(x+5/6)=0
11) (7/8-2x)(3x+1/3)=0
12)3x-2x^2=0
mk lưu nhầm ảnh ở bài dưới của câu
tìm x biết
a/x^3+3x^2+3x+2=0
b/x^4-2x^3+2x-1=0
c/x^4-3x^3-6x^2+8x=0
a ) \(x^3+3x^2+3x+2=0\)
\(\Leftrightarrow x^3+3x^2+3x+1+1=0\)
\(\Leftrightarrow\left(x+1\right)^3+1=0\)
\(\Leftrightarrow\left(x+1\right)^3=-1\)
\(\Leftrightarrow x+1=-1\)
\(\Leftrightarrow x=-2\)
Vậy \(x=-2\)
b ) \(x^4-2x^3+2x-1=0\)
\(\Leftrightarrow x^4-1-2x\left(x^2-1\right)=0\)
\(\Leftrightarrow\left(x^2-1\right)\left(x^2+1\right)-2x\left(x^2-1\right)=0\)
\(\Leftrightarrow\left(x^2-1\right)\left(x^2+1-2x\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x+1\right)\left(x-1\right)^2=0\)
\(\Leftrightarrow\left(x-1\right)^3\left(x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}\left(x-1\right)^3=0\\x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x-1=0\\x=-1\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-1\end{matrix}\right.\)
Vậy \(\left[{}\begin{matrix}x=1\\x=-1\end{matrix}\right.\)
a, \(x^3+3x^2+3x+2=0\)
\(\Leftrightarrow\left(x^3+2x^2\right)+\left(x^2+2x\right)+\left(x+2\right)=0\)
\(\Leftrightarrow\left(x+2\right)\left(x^2+x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x+2=0\\x^2+x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=-2\\x=0\end{matrix}\right.\)
b, \(x^4-2x^3+2x-1=0\)
\(\Leftrightarrow\left(x^4-x^3\right)-\left(x^3-x^2\right)-\left(x^2-x\right)+\left(x-1\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left[\left(x^3-x^2\right)\left(x-1\right)\right]=0\)
\(\Leftrightarrow\left(x-1\right)^3=0\)
\(\Leftrightarrow x=1\)
a ) x^3+3x^2+3x+2=0x3+3x2+3x+2=0
\Leftrightarrow x^3+3x^2+3x+1+1=0⇔x3+3x2+3x+1+1=0
\Leftrightarrow\left(x+1\right)^3+1=0⇔(x+1)3+1=0
\Leftrightarrow\left(x+1\right)^3=-1⇔(x+1)3=−1
\Leftrightarrow x+1=-1⇔x+1=−1
\Leftrightarrow x=-2⇔x=−2
Vậy x=-2x=−2
b ) x^4-2x^3+2x-1=0x4−2x3+2x−1=0
\Leftrightarrow x^4-1-2x\left(x^2-1\right)=0⇔x4−1−2x(x2−1)=0
\Leftrightarrow\left(x^2-1\right)\left(x^2+1\right)-2x\left(x^2-1\right)=0⇔(x2−1)(x2+1)−2x(x2−1)=0
\Leftrightarrow\left(x^2-1\right)\left(x^2+1-2x\right)=0⇔(x2−1)(x2+1−2x)=0
\Leftrightarrow\left(x-1\right)\left(x+1\right)\left(x-1\right)^2=0⇔(x−1)(x+1)(x−1)2=0
\Leftrightarrow\left(x-1\right)^3\left(x+1\right)=0⇔(x−1)3(x+1)=0
\Leftrightarrow\left[{}\begin{matrix}\left(x-1\right)^3=0\\x+1=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x-1=0\\x=-1\end{matrix}\right.⇔[(x−1)3=0x+1=0⇔[x−1=0x=−1
\Leftrightarrow\left[{}\begin{matrix}x=1\\x=-1\end{matrix}\right.⇔[x=1x=−1
Vậy \left[{}\begin{matrix}x=1\\x=-1\end{matrix}\right.[x=1x=−1
Giải phương trình
1) 16-8x=0
2) 7x+14=0
3) 5-2x=0
4) 3x-5=7
5) 8-3x=6
6) 8=11x+6
7)-9+2x=0
8) 7x+2=0
9) 5x-6=6+2x
10) 10+2x=3x-7
11) 5x-3=16-8x
12)-7-5x=8+9x
13) 18-5x=7+3x
14) 9-7x=-4x+3
15) 11-11x=21-5x
16) 2(-7+3x)=5-(x+2)
17) 5(8+3x)+2(3x-8)=0
18) 3(2x-1)-3x+1=0
19)-4(x-3)=6x+(x-3)
20)-5-(x+3)=2-5x
20) -5-(x + 3) = 2 - 5x ⇔ -5 - x - 3 = 2 -5x ⇔ 4x = 10 ⇔ x = \(\frac{5}{2}\)
Vậy...
1) 16 - 8x = 0 ⇔ 8(2 - x) = 0⇔ 2 - x = 0 ⇔ x = 2
Vậy phương trình có nghiệm là x = 2
Bài 1: Giải phương trình:
x4-6x3-x2+54x-72=0 (biết rằng phương trình có một nghiệm là x=2)
Bài 2: Giải các phương trình:
a) x4-5x2+4=0
b) x4-2x3-6x2+8x+8=0
c) 2x4-13x3+20x2-3x-2=0
GIẢI NHANH GIÚP MÌNH VỚI Ạ....THANKS MỌI NGƯỜI❤
1) \(x^4-6x^3-x^2+54x-72=0\)
\(\Leftrightarrow x^3\left(x-2\right)-4x^2\left(x-2\right)-9x\left(x-2\right)+36\left(x-2\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x^3-4x^2-9x+36\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left[x^2\left(x-4\right)-9\left(x-4\right)\right]=0\)
\(\Leftrightarrow\left(x-2\right)\left(x-4\right)\left(x^2-9\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x-4\right)\left(x-3\right)\left(x+3\right)=0\)
Tự làm nốt...
2) \(x^4-5x^2+4=0\)
\(\Leftrightarrow x^2\left(x^2-1\right)-4\left(x^2-1\right)=0\)
\(\Leftrightarrow\left(x^2-1\right)\left(x^2-4\right)=0\)
\(\Leftrightarrow\left(x-1\right)\left(x+1\right)\left(x-2\right)\left(x+2\right)=0\)
Tự làm nốt...
\(x^4-2x^3-6x^2+8x+8=0\)
\(\Leftrightarrow x^3\left(x-2\right)-6x\left(x-2\right)-4\left(x-2\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x^3-6x-4\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left[x^2\left(x+2\right)-2x\left(x+2\right)-2\left(x+2\right)\right]=0\)
\(\Leftrightarrow\left(x-2\right)\left(x+2\right)\left(x^2-2x-2\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(x+2\right)\left[\left(x-1\right)^2-\left(\sqrt{3}\right)^2\right]=0\)
\(\Leftrightarrow\left(x-2\right)\left(x+2\right)\left(x-1-\sqrt{3}\right)\left(x-1+\sqrt{3}\right)=0\)
...
\(2x^4-13x^3+20x^2-3x-2=0\)
\(\Leftrightarrow2x^3\left(x-2\right)-9x^2\left(x-2\right)+2x\left(x-2\right)+\left(x-2\right)=0\)
\(\Leftrightarrow\left(x-2\right)\left(2x^3-9x^2+2x+1\right)=0\)
Bí
\(2x^3-9x^2+2x+1\)
\(=2x^3-x^2-8x^2+4x-2x+1\)
\(=x^2\left(2x-1\right)-4x\left(2x-1\right)-\left(2x-1\right)\)
\(=\left(2x-1\right)\left(x^2-4x-1\right)\)
\(=\left(2x-1\right)\left(x^2-4x+4-5\right)\)
\(=\left(2x-1\right)\left[\left(x-2\right)^2-5\right]\)
.......