Tìm x bt:
a) x3+5x2−4x−20=0
Bài 5:
1) a) Cho hai đa thức:
P (x) = 5x2 + 3x3 - 5x2 + 2x3 – 2 +4x – 4x2 + x3
Q(x) = 6x – x3 + 5 – 4x3 + 6 – 3x2 – 7x2
Tính M(x) = P(x) + Q(x)
b) Tìm C(x) biết: (5x2 + 9x – 3x4 + 7x3 -12) + C(x) = -2x3 + 9 – 6x + 7x4 -2x3
2) Tìm nghiệm của các đa thức sau
a) 4x - b) x2 – 4x +3
a: P(x)=6x^3-4x^2+4x-2
Q(x)=-5x^3-10x^2+6x+11
M(x)=x^3-14x^2+10x+9
b: \(C\left(x\right)=7x^4-4x^3-6x+9+3x^4-7x^3-5x^2-9x+12\)
=10x^4-11x^3-5x^2-15x+21
Tìm x:
a) x3 +3x2 - 10x = 0
b) x3 - 5x2 - 14x =0
c) x3 + 5x2- 24x =0
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x3+3x2-10x=0
=>x(3+3.2-10)=0
=>x=0
x3-5x2-14x=0
=>x(3-5.2-14)=0
=>x=0
x3+5x2-24x=0
=>x(3+5.2-24)=0
=>x=0
Câu a)
\(x^3+3x^2-10=0\Rightarrow x\left(x^2+3x-10\right)=0\Rightarrow x\left(x^2-2x+5x-10\right)=0\Rightarrow x\left(x\left(x-2\right)+5\left(x-2\right)\right)=0\Rightarrow x\left(x+5\right)\left(x-2\right)=0\)
\(\Rightarrow x=0;x=5;x=2\)
Câu b:
\(x^3-5x^2-14x=0\Rightarrow x\left(x^2-5x-14\right)=0\Rightarrow x\left(x^2+2x-7x-14\right)=0\Rightarrow x\left(x\left(x+2\right)-7\left(x+2\right)\right)=0\Rightarrow x\left(x-7\right)\left(x+2\right)=0\)
\(\Rightarrow x=0;x=7;x=-2\)
Tìm đa thức M biết:
a) x 3 - 5 x 2 +x - 5 = (x - 5).M;
b) ( x 2 - 4x - 3).M = 2 x 4 - 13 x 3 + 14 x 2 + 15x.
1) Tìm GTNN của bt:
a)A=x2(x-1)2+2x2-4x-1
b)B=(x-5)(x-3)(x+2)(x+4)+2022
2) a) Phân tích đa thức thành nhân tử: x3-9x2+26x-24
b)Với n là số nguyên, cmr: 7n3-9n2+26n-12 chia hết cho 6
\(x^3-9x^2+26x-24\)
\(=x^3-4x^2-5x^2+20x+6x-24\)
\(=\left(x-4\right)\left(x^2-5x+6\right)\)
\(=\left(x-4\right)\left(x-2\right)\left(x-3\right)\)
1)tìm x bt:
a)7.2x=56
b)(2x+1)3=9.81
c)x3=82
d)4.2x-3=1
e)2.3x=162
a)7.2x=56⇔2x=8⇔2x=23⇔x=3
b)(2x+1)3=9.81⇔(2x+1)3=93⇔2x+1=9⇔2x=8⇔x=4
c)x3=82⇔x3=26⇔x=22⇔x=4
d)4.2x-3=1⇔4.2x=4⇔2x=1⇔2x=20⇔x=0
e)2.3x=162⇔3x=81⇔3x=34⇔x=4
Tìm x biết:
a) x 6 + 2 x 3 +1 = 0; b) x(x - 5) = 4x - 20;
c) x 4 -2 x 2 =8-4 x 2 ; d) ( x 3 - x 2 ) - 4 x 2 + 8x-4 = 0.
a) x = -1. b) x = 4 hoặc x = 5.
c) x = ± 2 . d) x = 1 hoặc x = 2.
x3 – 5x2 – x + 5 = 0
\(\Leftrightarrow\left(x-5\right)\left(x-1\right)\left(x+1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=5\\x=1\\x=-1\end{matrix}\right.\)
\(\Leftrightarrow x^2\left(x-5\right)-\left(x-5\right)=0\\ \Leftrightarrow\left(x^2-1\right)\left(x-5\right)=0\\ \Leftrightarrow\left[{}\begin{matrix}x=-1\\x=1\\x=5\end{matrix}\right.\)
\(x^3-5x^2-x+5=x^2\left(x-5\right)-\left(x-5\right)=\left(x-5\right)\left(x^2-1\right)=\left(x-5\right)\left(x-1\right)\left(x+1\right)\)
b) x3 – 5x2 – x + 5 = 0.
c) x3 – x2 – 25x + 25 = 0
d) 4x3 – 8x2 – 9x + 18 = 0.
b: \(\Leftrightarrow\left(x-5\right)\left(x+1\right)\left(x-1\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=5\\x=1\\x=-1\end{matrix}\right.\)
c: \(\Leftrightarrow\left(x-1\right)\left(x-5\right)\left(x+5\right)=0\)
\(\Leftrightarrow\left[{}\begin{matrix}x=1\\x=5\\x=-5\end{matrix}\right.\)
a) 5x(x – 2000) – x + 2000 = 0 b) 5x2 = 13x
c) x3+2x=0 d) x(x-5)= 5-x
e) (x+2)2 = x+2 f) x3 +4x =0
g)3x (x-10) =x-10 h) x(x+7) =4x+28
a) \(5x\left(x-2000\right)-x+2000=0\)
\(\Leftrightarrow5x\left(x-2000\right)-\left(x-2000\right)=0\)
\(\Leftrightarrow\left(5x-1\right)\left(x-2000\right)=0\)
\(\Leftrightarrow x\in\left\{\frac{1}{5};2000\right\}\)
b) \(5x^2=13x\)
\(\Leftrightarrow x\left(5x-13\right)=0\)
\(\Leftrightarrow x\in\left\{0;\frac{13}{5}\right\}\)
c) \(x^3+2x=0\)
\(\Leftrightarrow x\left(x^2+2\right)=0\)
Vì x^2+2 > 0 nên x = 0
Phân tích các đa thức sau thành nhân tử:
a) 5x-20xy
b) x2-9
c) x2-2xy+y2-z2
d) 5x.(x-1)-2.(x-1)
e) x2+4x+3
f) x3-x 3x2y+3xy2+y3-y
g) x2-x-y2-y
h) 16x-5x2-3
i) x3-4x
j) 2x2-6x
k) x3- 3x2-4x+12
l) x2-y2-5x+5y
Mn giúp em giải vs em cần gấp để lm bài kiểm tra.Em cảm ơn trc ạ