Tìm x, biết :
x - 45 - x : 5 = 35
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271-[(-43)+271+(-13)] = 56
40.(45-135)-40.(45+65)=-8000
32x+41=35-(-70) => x=2
tìm x thuộc z,y thuộc z biết:(x-1)(xy-5)=5 Chịu
a, \(\frac{x}{5}=\frac{-12}{20}\)
\(x=\frac{5.\left(-20\right)}{20}\)
\(x=-5\)
b, 3x - 35 = -45 - 2x
3x + 2x = -45 + 35
5x = -10
x = (-10) : 5
x = -2
c, \(\frac{-1}{6}-x=\frac{5}{12}+\frac{-2}{3}\)
\(\frac{-1}{6}-x=\frac{-1}{4}\)
\(-x=\frac{-1}{6}-\frac{-1}{4}\)
\(-x=\frac{1}{12}\)
\(x=\frac{-1}{12}\)
a: \(280-\left(x-140\right):35=270\)
=>(x-140):35=280-270=10
=>x-140=350
=>x=350+140
=>x=490
b: \(\left(190-2x\right):35-32=16\)
=>\(\left(190-2x\right):35=32+16=48\)
=>\(190-2x=35\cdot48=1680\)
=>2x=190-1680=-1490
=>x=-745
c: \(720:\left\lbrack41-\left(2x-5\right)\right\rbrack=2^3\cdot5\)
=>\(720:\left\lbrack41-\left(2x-5\right)\right\rbrack=8\cdot5=40\)
=>41-(2x-5)=720:40=18
=>2x-5=41-18=23
=>2x=28
=>x=14
d: \(\left(x:23+45\right)\cdot37-22=2^4\cdot105\)
=>\(\left(\frac{x}{23}+45\right)\cdot37=16\cdot105+22=1702\)
=>\(\frac{x}{23}+45=46\)
=>\(\frac{x}{23}=1\)
=>x=23
e: \(\left(3x-4\right)\left(x-1\right)^3=0\)
=>\(\left[\begin{array}{l}3x-4=0\\ x-1=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=\frac43\\ x=1\end{array}\right.\)
f: \(2^{2x-1}:4=8^3\)
=>\(2^{2x-1-2}=2^9\)
=>2x-3=9
=>2x=12
=>x=6
g: \(x^{17}=x\)
=>\(x^{17}-x=0\)
=>\(x\left(x^{16}-1\right)=0\)
=>\(\left[\begin{array}{l}x=0\\ x^{16}-1=0\end{array}\right.\Rightarrow\left[\begin{array}{l}x=0\\ x^{16}=1\end{array}\right.\Rightarrow\left[\begin{array}{l}x=0\\ x=1\\ x=-1\end{array}\right.\)
h: \(\left(x-5\right)^4=\left(x-5\right)^6\)
=>\(\left(x-5\right)^6-\left(x-5\right)^4=0\)
=>\(\left(x-5\right)^4\cdot\left\lbrack\left(x-5\right)^2-1\right\rbrack=0\)
=>\(\left(x-5\right)^4\cdot\left(x-4\right)\left(x-6\right)=0\)
=>x∈{4;5;6}
i: \(\left(x+2\right)^5=2^{10}\)
=>\(\left(x+2\right)^5=\left(2^2\right)^5=4^5\)
=>x+2=4
=>x=2
k: 1+2+3+...+x=78
=>\(\frac{x\left(x+1\right)}{2}=78\)
=>x(x+1)=156
=>\(x^2+x-156=0\)
=>(x+13)(x-12)=0
=>x=-13(loại) hoặc x=12(nhận)
l: \(\left(3x-2^4\right)\cdot7^3=2\cdot7^4\)
=>\(3x-16=2\cdot\frac{7^4}{7^3}=2\cdot7=14\)
=>3x=16+14=30
=>\(x=\frac{30}{3}=10\)
n: \(5^{x}:5^2=125\)
=>\(5^{x-2}=5^3\)
=>x-2=3
=>x=5
m: \(\left(x+1\right)^2=\left(x+1\right)^0\)
=>\(\left(x+1\right)^2=1\)
=>\(\left[\begin{array}{l}x+1=1\\ x+1=-1\end{array}\right.\Rightarrow\left[\begin{array}{l}x=0\\ x=-2\end{array}\right.\)
o: Số số hạng của dãy số 2;4;..;52 là:
(52-2):2+1=50:2+1=25+1=26(số)
Tổng của dãy số 2;4;...;52 là:
\(\left(52+2\right)\cdot\frac{26}{2}=54\cdot13=702\)
(2+x)+(4+x)+...+(52+x)=780
=>26x+702=780
=>26x=78
=>x=3
p: \(70=2\cdot5\cdot7;80=2^4\cdot5\)
=>ƯCLN(70;80)=\(2\cdot5=10\)
70⋮x; 80⋮x
=>x∈ƯC(70;80)
=>x∈Ư(10)
mà x>8
nên x=10
q: \(12=2^2\cdot3;25=5^2;30=2\cdot3\cdot5\)
=>BCNN(12;25;30)=\(2^2\cdot3\cdot5^2=300\)
x⋮12; x⋮25; x⋮30
=>x∈BC(12;25;30)
=>x∈B(300)
mà 0<x<500
nên x=300
Ta có x^35=x^45
<=>x^45-x^35=0
<=>x^35.(x^10-1)=0
<=> \(\orbr{\begin{cases}x^{35}=0\\x^{10}-1=0\end{cases}\Leftrightarrow\orbr{\begin{cases}x=0\\x^{10}=1\end{cases}\Leftrightarrow}\orbr{\begin{cases}x=0\\\orbr{\begin{cases}x=1\\x=-1\end{cases}}\end{cases}}}\)
35 . 34 + 35 . 38 + 65 . 75 + 65 . 45 + 35 . 34 =
= 35 . 34 + 35 . 38 + 35 . 34 + 65 . 75 + 65 . 45
= 35 . ( 34 + 38 + 34 ) + 65 . ( 75 + 45 )
= 35 . 110 + 65 . 110
= 110 . ( 35 + 65 )
= 110 . 100
= 11000
Hok tốt!!!!!!!!!!!!!
a) Tính bằng cách hợp lí nhất :
35 . 34 + 35 . 38 + 65 . 75 + 65 . 45 + 35 . 34
= 35 . 34 + 35 . 38 + 35 . 34 + 65 . 75 + 65 . 45
= 35 . ( 34 + 38 + 34 ) + 65 . ( 75 + 45 )
= 35 . 106 + 65 . 120
= 3710 + 7800
= 11510
3 . 25 . 8 + 4 . 37 . 6 + 2 . 38 . 12
= 3 . 8 . 25 + 4 . 6 . 37 + 2 . 12 . 38
= 24 . 25 + 24 . 37 + 24 . 38
= 24 . ( 25 + 37 + 38 )
= 24 . 100
= 2400
b) Tìm số tự nhiên x, biết :
( x - 5 ) ( x + 7 ) = 0
\(\Rightarrow\orbr{\begin{cases}x-5=0\\x+7=0\end{cases}\Rightarrow\orbr{\begin{cases}x=5\\x=-7\end{cases}}}.\)
Vậy .......
=>-4x=80
=>x=-20
x-45-x:5=35
x-45-x . 1/5=35
x.(1-1/5)=35+45
x.4/5=80
x=100
DẤU CHẤM LÀ NHÂN NHA!!!!