Tìm x biết
25 − 𝑥 = 6/16
56
Tìm x
100 : [2 . (x + 5) - 12] = -5
𝑥−(28−𝑥)=−56−73+105
56 - 6(x - 2)^3 = 440
2^x + 2^x+3 = 72
\(a,\Rightarrow2\left(x+5\right)-12=-20\\ \Rightarrow2\left(x+5\right)=-8\\ \Rightarrow x+5=-4\Rightarrow x=-9\\ b,\Rightarrow x-28+x=-24\\ \Rightarrow2x=4\Rightarrow x=2\\ c,\Rightarrow6\left(x-2\right)^3=-384\\ \Rightarrow\left(x-2\right)^3=-64=\left(-4\right)^3\\ \Rightarrow x-2=-4\Rightarrow x=-2\\ d,\Rightarrow2^x\left(1+2^3\right)=72\\ \Rightarrow2^x\cdot9=72\\ \Rightarrow2^x=8=2^3\Rightarrow x=3\)
a,⇒2(x+5)−12=−20⇒2(x+5)=−8⇒x+5=−4⇒x=−9b,⇒x−28+x=−24⇒2x=4⇒x=2c,⇒6(x−2)3=−384⇒(x−2)3=−64=(−4)3⇒x−2=−4⇒x=−2d,⇒2x(1+23)=72⇒2x⋅9=72⇒2x=8=23⇒x=3a,⇒2(x+5)−12=−20⇒2(x+5)=−8⇒x+5=−4⇒x=−9b,⇒x−28+x=−24⇒2x=4⇒x=2c,⇒6(x−2)3=−384⇒(x−2)3=−64=(−4)3⇒x−2=−4⇒x=−2d,⇒2x(1+23)=72⇒2x⋅9=72⇒2x=8=23⇒x=3
Tìm x , biết rằng
a) 𝑥3 - 64𝑥 = 0
b) 𝑥3 - 4𝑥2 = -4𝑥
c)𝑥2 - 16 - (𝑥 - 4) = 0
d)(2𝑥 + 1)2 = (3 + 𝑥)
e)𝑥3 - 6𝑥2 + 12𝑥 - 8 = 0
f)𝑥3 - 7𝑥 - 6 = 0
a) x³ - 64x = 0
x(x² - 64) = 0
x(x - 8)(x + 8) = 0
x = 0 hoặc x - 8 = 0 hoặc x + 8 = 0
*) x - 8 = 0
x = 8
*) x + 8 = 0
x = -8
Vậy x = -8; x = 0; x = 8
b) x³ - 4x² = -4x
x³ - 4x² + 4x = 0
x(x² - 4x + 4) = 0
x(x - 2)² = 0
x = 0 hoặc (x - 2)² = 0
*) (x - 2)² = 0
x - 2 = 0
x = 2
Vậy x = 0; x = 2
c) x² - 16 - (x - 4) = 0
(x - 4)(x + 4) - (x - 4) = 0
(x - 4)(x + 4 - 1) = 0
(x - 4)(x + 3) = 0
x - 4 = 0 hoặc x + 3 = 0
*) x - 4 = 0
x = 4
*) x + 3 = 0
x = -3
Vậy x = -3; x = 4
d) (2x + 1)² = (3 + x)²
(2x + 1)² - (3 + x)² = 0
(2x + 1 - 3 - x)(2x + 1 + 3 + x) = 0
(x - 2)(3x + 4) = 0
x - 2 = 0 hoặc 3x + 4 = 0
*) x - 2 = 0
x = 2
*) 3x + 4 = 0
3x = -4
x = -4/3
Vậy x = -4/3; x = 2
e) x³ - 6x² + 12x - 8 = 0
(x - 2)³ = 0
x - 2 = 0
x = 2
f) x³ - 7x - 6 = 0
x³ + 2x² - 2x² - 4x - 3x - 6 = 0
(x³ + 2x²) - (2x² + 4x) - (3x + 6) = 0
x²(x + 2) - 2x(x + 2) - 3(x + 2) = 0
(x + 2)(x² - 2x - 3) = 0
(x + 2)(x² + x - 3x - 3) = 0
(x + 2)[(x² + x) - (3x + 3)] = 0
(x + 2)[x(x + 1) - 3(x + 1)] = 0
(x + 2)(x + 1)(x - 3) = 0
x + 2 = 0 hoặc x + 1 = 0 hoặc x - 3 = 0
*) x + 2 = 0
x = -2
*) x + 1 = 0
x = -1
*) x - 3 = 0
x = 3
Vậy x = -1; x = -1; x = 3
a,x\(^3\)-64=0
x\(^3\) =64
=>x=3
b,x\(^3\)-4x\(^2\)=-4x
x\(^3\)-4x\(^2\)+4x=0
x(x\(^2\)-4x+4)=0
x(x-2)\(^2\)=)
TH1:x=0
TH2:x-2=0
=>x=2
c,x\(^2\)-16-(x-4)=0
(x+4)(x-4)-(x-4)=0
(x-4)(x+4-1)=0
(x-4)(x+3)=0
TH1:x-4=0
=>x=4
TH2:x+3=0
=>x=-3
d,(2x+1).2=3+x
4x+2-3-x=0
3x-1=0
x=\(\dfrac{1}{3}\)
e,x\(^3\)-6x\(^2\)+12x-8=0
(x-2)\(^3\)=0
=>x-2=0
=>x=2
f,x\(^3\)-7x+6=0
x\(^3\)-x-6x+6=0
x(x\(^2\)-1)-6(x-1)=0
x(x+1)(x-1)-6(x-1)=0
(x-1)(x\(^2\)+x-6)=0
TH1:x-1=0
=>x=1
TH2:x\(^2\)+x-6=0
x\(^2\)+3x-2x-6=0
x(x+3)-2(x+3)=0
(x+3)(x-2)=0
=>x+3=0 =>x-2=0
+>x=-3 =>x=2
d,(2x+1)\(^2\)=(3+x)\(^2\)
4x\(^2\)+4x+1-9-6x-x\(^2\)=0
3x\(^2\)-2x-8=0
3x\(^2\)-6x+4x-8=0
3x(x-2)+4(x-2)=0
(3x+4)(x-2)=0
TH1:3x+4=0 TH2:x-2=0
=>x=\(\dfrac{-4}{3}\) =>x=2
Bài 2: Tìm x biết
1. (𝑥 − 3)² = 4𝑥 ²+ 20x + 25
2. 2x(x – 4) + 𝑥² – 16 = 0
Lời giải:
1.
$(x-3)^2=4x^2+20x+25=(2x+5)^2$
$\Leftrightarrow (x-3)^2-(2x+5)^2=0$
$\Leftrightarrow (x-3-2x-5)(x-3+2x+5)=0$
$\Leftrightarrow (-x-8)(3x+2)=0$
$\Leftrightarrow -x-8=0$ hoặc $3x+2=0$
$\Leftrightarrow x=-8$ hoặc $x=-\frac{2}{3}$
2.
$2x(x-4)+x^2-16=0$
$\Leftrightarrow 2x(x-4)+(x-4)(x+4)=0$
$\Leftrightarrow (x-4)(2x+x+4)=0$
$\Leftrightarrow (x-4)(3x+4)=0$
$\Leftrightarrow x-4=0$ hoặc $3x+4=0$
$\Leftrightarrow x=4$ hoặc $x=-\frac{4}{3}$
Tìm giá trị của x
𝑥 +4/5 ×3/8=3/2
𝑥=2/5
𝑥=6/5
𝑥=16/5
𝑥 =72/40
\(x+\dfrac{4}{5}\times\dfrac{3}{8}=\dfrac{3}{2}\)
\(x+\dfrac{3}{10}=\dfrac{3}{2}\)
\(x=\dfrac{3}{2}-\dfrac{3}{10}\)
\(x=\dfrac{12}{10}=\dfrac{6}{5}\)
Tìm x
25/3×𝑥=5/6+4/3
A 𝑥=4
B 𝑥=325
C 𝑥=32518
D 𝑥=1350
(𝑥 – 2)^2 − (𝑥 − 3)(𝑥 + 3) = 6 tìm x
\(\Leftrightarrow x^2-4x+4-x^2+9=6\)
=>-4x=-7
hay x=7/4
b) (AMS 2007) Tìm x biết: (𝑥 + 4) + (𝑥 + 6) + (𝑥 + 8) + ⋯ + (𝑥 + 26) = 210
\(\left(x+4\right)+\left(x+6\right)+\left(x+8\right)+...+\left(x+26\right)=210\)
Số các chữ số x: \(\left(26-4\right):2+1=12\left(số\right)\)
\(\Rightarrow12x+\left(4+6+8+...+26\right)=210\)
\(\Rightarrow12x+\dfrac{\left(26+4\right)\left(\dfrac{26-4}{2}+1\right)}{2}=210\)
\(\Leftrightarrow12x+180=210\Leftrightarrow12x=30\Leftrightarrow x=\dfrac{5}{2}\)
(x + 4) + (x + 6) + (x + 8) + ... + (x + 26) = 210
<=> x[(26 - 4) : 2 + 1] + (26 + 4)[(26 - 4) : 2 + 1] : 2 = 210
<=> 12x + 180 = 210
<=> 12x = 210 - 180
<=> 12x = 30
<=> x = 2,5
Ta có: \(\left(x+4\right)+\left(x+6\right)+...+\left(x+26\right)=210\)
\(\Leftrightarrow12x=30\)
hay \(x=\dfrac{5}{2}\)
Tìm x
25/3×𝑥=5/6+4/3
A 𝑥=4
B 𝑥=32/5
C 𝑥=325/18
D 𝑥=13/50
\(\dfrac{25}{3}.x=\dfrac{5}{6}+\dfrac{4}{3}\)
\(\dfrac{25}{3}.x=\dfrac{13}{6}\)
\(x=\dfrac{13}{3}:\dfrac{25}{3}\)
\(x=\dfrac{39}{75}\)
Tìm x, biết.
𝑎) (𝑥−1)3+3𝑥(𝑥−4)+1=0
𝑏) (𝑥−1)(𝑥2+𝑥+1)=𝑥2(𝑥−9)+2𝑥2+6