Tìm x ,biết:
A, 3/5(2x-1/3)+4/15=12/30
B, (-0,2)^x=1/25
C,|x-1|-3/12=(-1/2)^2
Bài 3: Tìm x, biết:
a)(3x-5)(5-3x)+9(x+1)2=30
b)(x+4)2-(x+1)(x-1)=16
b. (x + 4)2 - (x + 1)(x - 1) = 16
<=> x2 + 4x + 16 - (x2 - 1) = 16
<=> x2 + 4x + 16 - x2 + 1 - 16 = 0
<=> x2 - x2 + 4x = 16 - 16 - 1
<=> 4x = -1
<=> x = \(\dfrac{-1}{4}\)
\(a,\Leftrightarrow-9x^2+30x-25+9x^2+18x+9=30\\ \Leftrightarrow48x=46\\ \Leftrightarrow x=\dfrac{23}{24}\\ b,\Leftrightarrow x^2+8x+16-x^2+1=16\\ \Leftrightarrow8x=-1\Leftrightarrow x=-\dfrac{1}{8}\)
Tìm x, biết:
a) x + 15 = 34 : 3 + 8
b) 15 - (12 - x) = 22.
c) 4.(2x – 1) mũ 2 = 100
d) 2.3 mũ x – 16 = 146
tìm x,biết:
a, 3(x-3)-6x=0
b, 2x(x-15)+2x
c, 2(x-3)+3x=9
d, x(x-11)+2(x-11)=0
e,x(x+2)+8=x^2
f, 8(x+1)+2x=-2
g,12-3(x+2)=0
a: \(3\left(x-3\right)-6x=0\)
=>\(3x-9-6x=0\)
=>-3x-9=0
=>3x+9=0
=>3x=-9
=>\(x=-\dfrac{9}{3}=-3\)
b: Đề thiếu vế phải rồi bạn
c: \(2\left(x-3\right)+3x=9\)
=>2x-6+3x=9
=>5x-6=9
=>5x=6+9=15
=>x=15/5=3
d: \(x\left(x-11\right)+2\left(x-11\right)=0\)
=>\(\left(x-11\right)\left(x+2\right)=0\)
=>\(\left[{}\begin{matrix}x-11=0\\x+2=0\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=11\\x=-2\end{matrix}\right.\)
e: \(x\left(x+2\right)+8=x^2\)
=>\(x^2+2x+8=x^2\)
=>2x+8=0
=>2x=-8
=>x=-8/2=-4
f: \(8\left(x+1\right)+2x=-2\)
=>\(8x+8+2x=-2\)
=>10x=-2-8=-10
=>\(x=-\dfrac{10}{10}=-1\)
g: 12-3(x+2)=0
=>3(x+2)=12
=>x+2=12/3=4
=>x=4-2=2
1.Thực hiện các phép tính sau :
a) \(-\dfrac{4}{3}.\dfrac{5}{12}+\dfrac{1}{3}.\dfrac{5}{12}\) b)\(3\dfrac{1}{5}+\left(\dfrac{2}{7}-\dfrac{7}{2}\right):\dfrac{3}{28}\)
2.Tìm x, biết:
a) 2x+19=\(^{5^2}\) b)\(-\dfrac{2}{9}x-\dfrac{1}{7}=\dfrac{4}{21}\)
1,
a, \(\left(\dfrac{-4}{3}+\dfrac{1}{3}\right).\dfrac{5}{12}\)=-\(\dfrac{5}{12}\)
b, \(\dfrac{16}{5}+\left(\dfrac{-45}{14}\right):\dfrac{3}{28}\)
=\(\dfrac{-2}{15}\)
2,
a, 2x+19=25
=>x=3
b, \(-\dfrac{2}{9}x=\dfrac{1}{3}\)
=>x=\(\dfrac{-3}{2}\)
Bài 1:
a) Ta có: \(\dfrac{-4}{3}\cdot\dfrac{5}{12}+\dfrac{1}{3}\cdot\dfrac{5}{12}\)
\(=\dfrac{5}{12}\cdot\left(\dfrac{-4}{3}+\dfrac{1}{3}\right)\)
\(=\dfrac{-5}{12}\)
b) Ta có: \(3\dfrac{1}{5}+\left(\dfrac{2}{7}-\dfrac{7}{2}\right):\dfrac{3}{28}\)
\(=\dfrac{16}{5}+\left(\dfrac{4}{14}-\dfrac{49}{14}\right):\dfrac{3}{28}\)
\(=\dfrac{16}{5}+\dfrac{-45}{14}\cdot\dfrac{28}{3}\)
\(=\dfrac{16}{5}-30=\dfrac{-134}{5}\)
1)
a) \(-\dfrac{4}{3}.\dfrac{5}{12}+\dfrac{1}{3}.\dfrac{5}{12}=\dfrac{5}{12}.\left(\dfrac{-4}{3}+\dfrac{1}{3}\right)=\dfrac{5}{12}.\left(-1\right)=-\dfrac{5}{12}\)
b) \(3\dfrac{1}{5}+\left(\dfrac{2}{7}-\dfrac{7}{2}\right).\dfrac{28}{3}=3+\dfrac{1}{5}-\dfrac{45}{14}.\dfrac{28}{3}\)
\(=3+\dfrac{1}{5}-30=-27+\dfrac{1}{5}=-\dfrac{134}{5}\)
2)
a) \(2x+19=25\)
\(2x=25-19=6\)
\(x=3\)
b) \(-\dfrac{2}{9}x-\dfrac{1}{7}=\dfrac{4}{21}\)
\(-\dfrac{2x}{9}=\dfrac{4}{21}+\dfrac{1}{7}=\dfrac{1}{3}\)
\(x=\dfrac{1}{3}.\left(-\dfrac{9}{2}\right)=-\dfrac{3}{2}\)
Bài 2: Tìm số tự nhiên x, biết:
a) 100-7(x-5)=58 b) 12(x-1):3=43+23
c) 24+5x=75:73 d)5.(x-1)-206=24.4
e) 5(x-4)2-7=13 f) (x+1)+(x+2)+....+(x+30)=795
g) 2x+3 - 3.2x+1=32 h) 221-(3x+2)3=96
Mn bày e gấp
a: Ta có: \(100-7\left(x-5\right)=58\)
\(\Leftrightarrow7\left(x-5\right)=42\)
\(\Leftrightarrow x-5=6\)
hay x=11
b: Ta có: \(12\left(x-1\right):3=4^3+2^3\)
\(\Leftrightarrow12\left(x-1\right)=216\)
\(\Leftrightarrow x-1=18\)
hay x=19
1/ Thực hiện phép nhân :
a) x2 ( 5x3 - x - \(\dfrac{1}{2}\))
b) ( 3xy - x2 + y ) \(\dfrac{2}{3}\)x2y
c) x2 ( 4x3 - 5xy + 2x ) ( -\(\dfrac{1}{2}\) xy )
2/ Tìm x, biết
a) 3x( 12x - 4 ) - 9x (4x - 3 ) = 30
b ) x( 5 - 2x ) + 2x ( x - 1 )= 15
2.
a. 3x(12x - 4) - 9x(4x - 3) = 30
<=> 36x2 - 12x - 36x2 + 27x = 30
<=> 36x2 - 36x2 - 12x + 27x = 30
<=> 15x = 30
<=> x = 2
b. x(5 - 2x) + 2x(x - 1) = 15
<=> 5x - 2x2 + 2x2 - 2x = 15
<=> -2x2 + 2x2 + 5x - 2x = 15
<=> 3x = 15
<=> x = 5
a) x2 ( 5x3 - x - 2323x2y= 6969x3y2- 2323x4y+ 2323x2y2
c) x2 ( 4x3 - 5xy + 2x ) ( -
1, Tìm số nguyên x, biết:
a, x - 17 = 23
b, 2(x - 1) = 7 + (-3)
c, 4.(x + 5)3 - 7 = 101
d, 2x+1 .3 + 15 = 39
1)
\(x-17=23\\ \Rightarrow x=23+17\\ \Rightarrow x=40\)
2)
\(2\left(x-1\right)=7+\left(-3\right)\\ \Rightarrow2x-2=4\\ \Rightarrow2x=4+2\\ \Rightarrow2x=8\\ \Rightarrow x=4\)
3)
\(4\left(x+5\right)^3-7=101\\ \Rightarrow4\left(x+5\right)^3=101+7\\ \Rightarrow4\left(x+5\right)^3=108\\ \Rightarrow\left(x+5\right)^3=108\div4\\ \Rightarrow\left(x+5\right)^3=27\\ \Rightarrow\left(x+5\right)^3=3^3\\ \Rightarrow x+5=3\Rightarrow x=3-5\\ \Rightarrow x=-2\)
4)
\(2^{x+1}\times3+15=39\\ \Rightarrow2^{x+1}\times3=39-15\\ \Rightarrow2^{x+1}\times3=24\\ \Rightarrow2^{x+1}=24\div3\\ \Rightarrow2^{x+1}=8\)
\( \Rightarrow2^{2+1}=8\\\Rightarrow2^3=8\Rightarrow x=2 \)
a) x - 17 = 23
x = 23 + 17
x = 40
Vậy x = 40
b) 2 ( x - 1 ) = 7 + ( - 3 )
x - 1 = 4 : 2
x = 2 + 1
x = 3
Vậy x = 3
c) 4 ( x + 3 )^3 - 7 = 101
4 ( x + 3 )^3 = ( 101 + 7 ) : 4
( x + 3 )^3 = 3^3
⇒ x + 3 = 3
⇒ x = 0
Vậy x = 0
d) 2^{ x+ 1 } . 3 + 15 = 39
2^{ x + 1 } = ( 39 - 15 ) : 3
2^{ x + 1 } = 2{ 2 + 1 }
⇒ x + 1 = 2 + 1
⇒ x = 2
Vậy x = 2
Bài 1: Tìm số nguyên x biết:
a)12 - 5x = 37
b)7 - 3| x - 2| = -11
c)x + 2/8 = -15/4
a) Ta có: 12-5x=37
\(\Leftrightarrow5x=-25\)
hay x=-5
Vậy: x=-5
b) Ta có: 7-3|x-2|=-11
\(\Leftrightarrow3\left|x-2\right|=18\)
\(\Leftrightarrow\left|x-2\right|=6\)
\(\Leftrightarrow\left[{}\begin{matrix}x-2=6\\x-2=-6\end{matrix}\right.\Leftrightarrow\left[{}\begin{matrix}x=8\\x=-4\end{matrix}\right.\)
Vậy: \(x\in\left\{8;-4\right\}\)
c) Ta có: \(x+\dfrac{2}{8}=-\dfrac{15}{4}\)
\(\Leftrightarrow x=\dfrac{-15}{4}-\dfrac{2}{8}=\dfrac{-15}{4}-\dfrac{1}{4}\)
hay x=-4
Vậy: x=-4
a, \(\Leftrightarrow5x=12-37=-25\)
\(\Leftrightarrow x=-\dfrac{25}{5}=-5\)
Vậy ...
b, \(\Leftrightarrow3\left|x-2\right|=7+11=18\)
\(\Leftrightarrow\left|x-2\right|=\dfrac{18}{3}=6\)
\(\Leftrightarrow\left[{}\begin{matrix}x-2=6\\x-2=-6\end{matrix}\right.\)
\(\Leftrightarrow\left[{}\begin{matrix}x=8\\x=-4\end{matrix}\right.\)
Vậy ...
c, \(\Leftrightarrow x=-\dfrac{15}{4}-\dfrac{2}{8}=-4\)
Vậy ..
a)-5; b)8 hoặc -4;c)-4 nhé. Bn tham khảo nhé
Bài 2: Tìm x, biết:
a) 75 - (x + 11) = 13
b) 29 + (x + 11) = 57
c) 11 + x : 5 = 13
d) 13 + 2(x + 1) = 15
e) 2x + 21 = 41
f) 12 + 3(x – 2) = 60
g) 24x – 11.13 = 11.11
h) 17 – (x – 4) : 2 = 3
c: Ta có: 11+x:5=13
\(\Leftrightarrow x:5=2\)
hay x=10
d: Ta có: \(13+2\left(x+1\right)=15\)
\(\Leftrightarrow2x+2=2\)
\(\Leftrightarrow2x=0\)
hay x=0
e: Ta có: 2x+21=41
\(\Leftrightarrow2x=20\)
hay x=10
f: Ta có: \(12+3\left(x-2\right)=60\)
\(\Leftrightarrow3\left(x-2\right)=48\)
\(\Leftrightarrow x-2=16\)
hay x=18
g: Ta có: \(24x-11\cdot13=11\cdot11\)
\(\Leftrightarrow24x=11\cdot24\)
hay x=11
h: Ta có: \(17-\left(x-4\right):2=3\)
\(\Leftrightarrow\left(x-4\right):2=14\)
\(\Leftrightarrow x-4=28\)
hay x=32