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Tính
a) đáp án là 90
b)đáp án là âm 9
c)đáp án là âm 10
tìm x
a) xbằng 5
b) x bằng 3
c) x bằng 3
a) pt <=> \(\frac{x\left(x+1\right)}{2}=500500\)
<=> \(x^2+x=1001000\)
<=> \(x^2-1000x+1001x-1001000=0\)
<=> \(\left(x-1000\right)\left(x+1001\right)=0\)
<=> \(\orbr{\begin{cases}x=1000\\x=-1001\end{cases}}\)
Do \(x>0\)=> \(x=1000\)
b)
<=> \(2x=210\)
<=> \(x=105\)
c)
<=> \(6x-81=3.7\)
<=> \(x=17\)
d)
<=> \(125-5\left(3x-1\right)=5^2\)
<=> \(5\left(3x-1\right)=100\)
<=> \(3x-1=20\)
<=> \(x=7\)
e)
<=> \(4^{x+1}+1=65\)
<=> \(4^{x+1}=64\)
<=> \(x+1=3\)
<=> \(x=2\)
j)
<=> \(2\left(2x-3\right)=14\)
<=> \(2x-3=7\)
<=> \(x=5\)
Câu 2:
a: \(=9\cdot8-72:4=72-18=54\)
b: \(=125\cdot26+125\cdot32+125\cdot42\)
\(=125\left(26+32+42\right)=125\cdot100=12500\)
c: \(=5871:\left(928-825\right)+1=5871:103+1=57+1=58\)
d: \(=2012+78-178-2012=-100\)
a) \(9\cdot2^3-72:2^2\)
\(=72-18=54\)
b) \(125\cdot26+5^3\cdot32+25\cdot42\cdot5\)
\(=125\cdot26+125\cdot32+125\cdot42\)
\(=125\cdot\left(26+32+42\right)=125\cdot100=12500\)
c) \(5871:\left[928-\left(247-82\right)\cdot5\right]+2012^0\)
\(=5871:\left[928-\left(247-82\right)\cdot5\right]+1\)
\(=5871:\left(928-165\cdot5\right)+1\)
\(=5871:103+1\)
\(=58\)
d) \(2012+78+\left(-178\right)+\left(-2012\right)\)
\(=\left[2012+\left(-2012\right)\right]+\left[78+\left(-178\right)\right]\)
\(=-100\)
a, \(9.2^3-\frac{72}{2^2}=9.8-\frac{72}{4}=72-18=54\)
b, \(125.26+5^3.32+25.42.5\)
\(=125.26+125.32+125.42\)
\(=125.\left(26+32+42\right)\)
\(=125.100\)
\(=12500\)
c, \(\frac{5871}{\left[928-\left(247-82\right).5\right]}+2012^0\)
\(=\frac{5871}{103}+1\)
\(=57+1\)
\(=58\)
d, \(2012+78+\left(-178\right)+\left(-2012\right)\)
\(=\left[2012+\left(-2012\right)\right]+\left[78+\left(-178\right)\right]\)
\(=0+100\)
\(=100\)
a,10+2x=45:43
10+2x=42
10+2x=16
2x=16-10
2x=6
x=6:2
x=3
b,310-(20-x)=300
20-x =310-300
20-x =10
x=20-10
x=10
c,4x+1+40=65
4x+1+40=65
4x+1+1 =65
4x+1 =65-1
4x+1 =64
4x+1 =43
x =3-1
=> x =2
a) 10 + 2x = 45 : 43
10 + 2x = 42 = 16
2x = 16 - 10
2x = 6
x = 3
b) 310 - (20 - x) = 300
310 - 20 + x = 300
290 + x = 300
x = 300 - 290
x = 10
c) 4x + 1 + 40 = 65
4x + + 1 = 65
4x + 1 = 64 = 43
=> x + 1 = 3
=> x = 2
a) \(x^{20}=x\)
\(\Rightarrow\orbr{\begin{cases}x=0\\x=1\end{cases}}\)
b) \(x^6:x^3=125\)
\(\Leftrightarrow x^{6-3}=125\)
\(\Leftrightarrow x^3=125\)
\(\Leftrightarrow x^3=5^3\)
\(\Leftrightarrow x=5\)
c) \(4x^3+12=120\)
\(\Leftrightarrow4x^3=120-12\)
\(\Leftrightarrow4x^3=108\)
\(\Leftrightarrow x^3=27\)
\(\Leftrightarrow x^3=3^3\)
\(\Leftrightarrow x=3\)
d) \(x^{10}=x^1\)
\(\Leftrightarrow x^{10}=x\)
\(\Rightarrow\orbr{\begin{cases}x=1\\x=0\end{cases}}\)
e) \(\left(2x-15\right)^5=\left(2x-15\right)^3\)
\(\Leftrightarrow\left(2x-15\right)^5-\left(2x-15\right)^3=0\)
\(\Leftrightarrow\left(2x-15\right)^3\left[\left(2x-15\right)^2-1\right]=0\)
\(\Rightarrow\orbr{\begin{cases}\left(2x-15\right)^3=0\\\left(2x-15\right)^2-1=0\end{cases}}\)
\(\Rightarrow\orbr{\begin{cases}2x-15=0\\\orbr{\begin{cases}2x-15=1\\2x-15=-1\end{cases}}\end{cases}}\Rightarrow\orbr{\begin{cases}x=\frac{15}{2}\\\orbr{\begin{cases}x=8\\x=-7\end{cases}}\end{cases}}\)\(\Rightarrow2x-15=0\)hoặc \(2x-15=1\) hoặc \(2x-15=-1\)
\(\Rightarrow x=\frac{15}{2}\)hoặc \(x=8\)hoặc \(x=7\)
Bài 1:
a,(2x-15):13+51=64
=> (2x-15):13=64-51
=> (2x-15):13=13
=>(2x-15)=1
=> 2x =16
=> x = 8
Vậy: x= 8
1)=>3(x-5)(2x+9)+3(x-5)=0=>(x-5)(6x+30)
=>x-5=0=>x=5
6x+30=0=>x=-5
2)=>x^2-16=0=>x=+-4
12-4x=0=>x=3
3)=>9-x^2=0=>x=+-3
4x-8=0=>x=2
4)=>8-x^3=0=>x=3
5^x-125=0=>x=2
5)=>2^x.2^x=8=>2^2x=8=>2x=3=>x=1,5
a) \(6x-36=5^{12}:5^{10}-2012^0\)
\(6x-36=5^2-2012^0\)
\(6x-36=25-1\)
\(6x-36=24\)
\(6x\) \(=24+36\)
\(6x\) \(=60\)
\(x=60:6\)
\(x=10\)
Vậy \(x=10\)
b) \(2x-125=-65\)
\(2x\) \(=\left(-65\right)+125\)
\(2x\) \(=60\)
\(x=60:2\)
\(x=30\)
Vậy \(x=30\)
c) \(2012-120\left(4x+1\right)=932\)
\(120\left(4x+1\right)=2012-932\)
\(120\left(4x+1\right)=1080\)
\(4x+1=1080:120\)
\(4x+1=9\)
\(4x\) \(=9-1\)
\(4x\) \(=8\)
\(x=8:4\)
\(x=2\)
Vậy \(x=2\)
a) 6x - 36 = 512 : 510 - 20120
6x - 36 = 52 - 20120
6x - 36 = 25 - 1
6x - 36 = 24
6x = 24 + 36
6x = 60
x = 60 : 6
x = 10
Vậy x = 10
b) 2x - 125 = -65
2x = (-65) + 125
2x = 60
x = 60 : 2
x = 30
Vậy x = 30
c) 2012 - 120(4x + 1) = 932
120(4x + 1) = 2012 - 932
120(4x + 1) = 1080
4x + 1 = 1080 : 120
4x + 1 = 9
4x = 9 - 1
4x = 8
x = 8 : 4
x = 2
Vậy x = 2.
Chúc bạn học tốt!