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L
17 tháng 4 2022
a. M(x) + N(x) = 3x3 - 3x + x2 + 5 + 2x2 - x + 3x3 + 9
= (3x3 + 3x3) + ( x2 + 2x2 ) + ( -3x - x ) + (5 + 9)
= 6x3 + 3x2 - 4x + 14
b. M(x) + N(x) - P(x) = 6x3 + 3x2 + 2x
=> 6x3 + 3x2 - 4x + 14 - P(x) = 6x3 + 3x2 + 2x
=> 6x3 + 3x2 - 4x + 14 - ( 6x3 + 3x2 + 2x) = P(x)
=> 6x3 + 3x2 - 4x + 14 - 6x3 - 3x2 - 2x = P(x)
=> (6x3 - 6x3 ) + (3x2 - 3x2 ) + (-4x - 2x ) + 14 = P(x)
=> -6x + 14 = P(x)
Ta có : -6x + 14 = 0
=> -6x = -14
=> x = 7/3
=> Đa thức P(x) = -6x + 14 có nghiệm là 7/3
=>
PL
0
DT
1
BH
16 tháng 7 2016
\(C=\frac{x}{x-3}-\frac{x^2+3x}{2x+3}\left(\frac{x+3}{x^2-3x}-\frac{x}{x^2-9}\right)\)
=>\(C=\frac{x}{x-3}-\frac{x\left(x+3\right)}{2x+3}.\left[\frac{x+3}{x\left(x-3\right)}-\frac{x}{\left(x-3\right)\left(x+3\right)}\right]\)
=>\(C=\frac{x}{x-3}-\frac{x\left(x+3\right)}{2x+3}\left[\frac{\left(x+3\right)^2}{x\left(x-3\right)\left(x+3\right)}-\frac{x^2}{x\left(x-3\right)\left(x+3\right)}\right]\)
=>\(C=\frac{x}{x-3}-\frac{x\left(x+3\right)}{2x+3}.\frac{\left(x+3\right)^2-x^2}{x\left(x-3\right)\left(x+3\right)}\)
=>\(C=\frac{x}{x-3}-\frac{x\left(x+3\right)}{2x+3}.\frac{\left(x+3-x\right)\left(x+3+x\right)}{x\left(x-3\right)\left(x+3\right)}\)
=>\(C=\frac{x}{x-3}-\frac{x\left(x+3\right)}{2x+3}.\frac{3\left(2x+3\right)}{x\left(x-3\right)\left(x+3\right)}\)
=>\(C=\frac{x}{x-3}-\frac{3}{x-3}\)
=>\(C=\frac{x-3}{x-3}\)
=>C=1
1 tháng 2 2018
(x−3)(x2+3x+9)−(3x−17)=x3−12
⇒x(x2+3x+9)−3(x2+3x+9)−3x+17=x3−12
⇒x3+3x2+9x−3x2−9x−27−3x+17=x3−12
⇒x3+(3x2−3x2)+(9x−9x)−3x−10=x3+12
⇒x3−3x−10=x3+12
⇒x3−3x−10−12=x3
⇒x3−3x−22=x3
⇒3x−22=0
⇒3x=22⇒x=223
1 tháng 2 2018
(x−3)(x^2+3x+9)−(3x−17)=x^3−12
⇔x^3−27−3x+17=x^3−12
⇔−10−3x=−12
⇔3x=2
⇔x=2/3
Vậy...
ND
Nguyễn Đức Trí
VIP
31 tháng 7 2023
\(4.3^x+3^{x+1}=63\)
\(\Rightarrow4.3^x+3.3^x=63\)
\(\Rightarrow7.3^x=63\Rightarrow3^x=9=3^2\Rightarrow x=2\)
\(9.\left(\dfrac{2}{3}\right)^{x+2}-\left(\dfrac{2}{3}\right)^x=\dfrac{4}{3}\)
\(\Rightarrow9.\left(\dfrac{2}{3}\right)^2\left(\dfrac{2}{3}\right)^x-\left(\dfrac{2}{3}\right)^x=\dfrac{4}{3}\)
\(\Rightarrow9.\dfrac{4}{9}^{ }.\left(\dfrac{2}{3}\right)^x-\left(\dfrac{2}{3}\right)^x=\dfrac{4}{3}\)
\(\Rightarrow\left(\dfrac{2}{3}\right)^x.\left(4-1\right)=\dfrac{4}{3}\)
\(\Rightarrow\left(\dfrac{2}{3}\right)^x.\dfrac{1}{3}=\dfrac{4}{3}\Rightarrow\left(\dfrac{2}{3}\right)^x=4\)
mà \(0< \left(\dfrac{2}{3}\right)^x< 1;4>0;x>0\)
\(\Rightarrow x\in\varnothing\)
16 tháng 6 2023
`@` `\text {Ans}`
`\downarrow`
`a)`
`3x(4x-1) - 2x(6x-3) = 30`
`=> 12x^2 - 3x - 12x^2 + 6x = 30`
`=> 3x = 30`
`=> x = 30 \div 3`
`=> x=10`
Vậy, `x=10`
`b)`
`2x(3-2x) + 2x(2x-1) = 15`
`=> 6x- 4x^2 + 4x^2 - 2x = 15`
`=> 4x = 15`
`=> x = 15/4`
Vậy, `x=15/4`
`c)`
`(5x-2)(4x-1) + (10x+3)(2x-1) = 1`
`=> 5x(4x-1) - 2(4x-1) + 10x(2x-1) + 3(2x-1)=1`
`=> 20x^2-5x - 8x + 2 + 20x^2 - 10x +6x - 3 =1`
`=> 40x^2 -17x - 1 = 1`
`d)`
`(x+2)(x+2)-(x-3)(x+1)=9`
`=> x^2 + 2x + 2x + 4 - x^2 - x + 3x + 3=9`
`=> 6x + 7 =9`
`=> 6x = 2`
`=> x=2/6 =1/3`
Vậy, `x=1/3`
`e)`
`(4x+1)(6x-3) = 7 + (3x-2)(8x+9)`
`=> 24x^2 - 12x + 6x - 3 = 7 + (3x-2)(8x+9)`
`=> 24x^2 - 12x + 6x - 3 = 7 + 24x^2 +11x - 18`
`=> 24x^2 - 6x - 3 = 24x^2 + 18x -11`
`=> 24x^2 - 6x - 3 - 24x^2 + 18x + 11 = 0`
`=> 12x +8 = 0`
`=> 12x = -8`
`=> x= -8/12 = -2/3`
Vậy, `x=-2/3`
`g)`
`(10x+2)(4x- 1)- (8x -3)(5x+2) =14`
`=> 40x^2 - 10x + 8x - 2 - 40x^2 - 16x + 15x + 6 = 14`
`=> -3x + 4 =14`
`=> -3x = 10`
`=> x= - 10/3`
Vậy, `x=-10/3`
LM
Lê Minh Vũ
CTVHS
VIP
21 tháng 6 2023
\(2\left(3x-2\right)-3\left(x-2\right)=-1\)
\(6x-4-3x+6=-1\)
\(3x+2=-1\)
\(3x=-1-2\)
\(3x=-3\)
\(x=-1\)
\(2\left(3-3x^2\right):3x\left(2x-1\right)=9\)
\(6-6x^2:6x^2-3x=9\)
\(6-x^2-3x=9\)
\(-x^2-3x+6=9\)
\(-x^2-3x=5\)
\(-x\left(x+3\right)=5\)
\(x=-5;x=2\)
HL
7 tháng 2 2022
a) \(\text{}/3x-5/-\frac{1}{7}=\frac{1}{3}\) b)\(\left(\frac{3}{5}x-\frac{2}{3}x-x\right).\frac{1}{7}=\frac{-5}{21}\)
\(/3x-5/=\frac{10}{21}\) \([x.\left(\frac{3}{5}-\frac{2}{3}-1\right)]=\frac{-5}{21}.7\)
\(\Rightarrow3x-5=\frac{10}{21}hay3x-5=\frac{-10}{21}\) \(\left[x.\frac{-16}{15}\right]=\frac{-5}{3}\)
\(3x=\frac{115}{21}\) \(3x=\frac{95}{21}\) \(x=\frac{25}{16}\)
\(x=\frac{115}{63}\) \(x=\frac{95}{63}\) Vậy x = \(\frac{25}{16}\)
Vậy x \(\in\left\{\frac{115}{63};\frac{95}{63}\right\}\)
`@` `\text {Ans}`
`\downarrow`
Thực hiện phép tính ;-;?
\((x+3) (x^2-3x+9) + (x-3) ( x^2+3x+9 )\)
`= x(x^2 - 3x + 9) + 3(x^2 - 3x + 9) + x(x^2 + 3x + 9) - 3(x^2 + 3x + 9)`
`= x^3 - 3x^2 + 9x + 3x^2 - 9x + 27 + x^3 + 3x^2 + 9x - 3x^2 - 9x - 27`
`= (x^3 + x^3) + (-3x^2 + 3x^2 + 3x^2 - 3x^2) + (9x - 9x + 9x - 9x) + (27 - 27)`
`= 2x^3`
=x3+33+x3-33
=2x3