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Áp dụng công thức tính dãy số ta có
\(\left(x+1\right).\left[\left(x-1\right):1+1\right]:2=666\)
\(\Rightarrow\left(x+1\right)x=1332\)
\(\Rightarrow x^2+x-1332=0\)
\(\Rightarrow x^2+37x-36x-1332=0\)
\(\Rightarrow x\left(x+37\right)-36\left(x+37\right)=0\)
\(\Rightarrow\left(x+37\right)\left(x-36\right)=0\)
\(\Rightarrow\orbr{\begin{cases}x+37=0\\x-36=0\end{cases}\Rightarrow\orbr{\begin{cases}x=-37\\x=36\end{cases}}}\)
\(\Rightarrow x=36\)
<=> (x+1).[(x-1):1+1]:2=666
<=> (x+1).x:2=666
<=>(x+1).x=666.2
<=>( x+1).x=1332
<=>(x+1).x=37.36
<=>x=36
Vậy x=36
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106105 - 150 : x = 386
150 : x = 106105 - 386
150 : x = 105719
x = 150 : 105719
x = 150/105719
44820 : x = 83 . 5
44820 : x = 415
x = 44820 : 415
x = 108
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y x 5 - 6 =1,9 x 3
y x 5 - 6 = 5,7
y x 5 = 5,7 + 6
y x 5 = 11,7
y = 11,7 : 5
y= 2,34
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2+3/4=11/4 ; 2-3/5=7/5
5/7:6=5/42 ; 5+2/7=37/7
Bài 2: a) x-1/6=1/2+1/3
x-1/6=5/6
x=5/6+1/6
x=1
b) x+1/8=1/2-1/3
x+1/8=1/6
x=1/6-1/8
x=1/24
c) x:1/2=2/3.3/4
x:1/2=1/2
x=1/2.1/2
x =1/4
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a) (3 + 6 + 9 + ... + 303) x (245 - 49 x 5)
(3 + 6 + 9 + ... + 303) x (245 - 245)
(3 + 6 + 9 + ... + 303) x 0 = 0
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a.
(1 + 3 + 5 + ... + 2007 + 2009 + 2011) x (125125 x 127 - 127127 x 125)
= (1 + 3 + 5 + ... + 2007 + 2009 + 2011) x 0
= 0
b.
\(\frac{2006\times125+1000}{126\times2006-1006}=\frac{2006\times125+1000}{125\times2006+1\times2006-1006}=\frac{2006\times125+1000}{125\times2006+1000}=1\)
a,
( 1+3+5+7+…+2003+2005) x (125 125 x 127 – 127 127 x 125)
= ( 1+3+5+7+…+2003+2005) x (125 x 1001 x 127 – 127 x 1001x 125)
= ( 1+3+5+7+…+2003+2005) x 0 = 0
![](https://rs.olm.vn/images/avt/0.png?1311)
Ta có: 8,75xX+1,25xX=20
Xx(8,75+1,25)=20
Xx10=20
X=20:10=2
Vậy X=2
Mọi người tk cho mình nha. Mình cảm ơn nhiều ^.< ( Cô bé tháng 1 )
\(\left(x+1\right)+\left(x+3\right)+\left(x+5\right)=30\)
\(x+x+x+\left(1+3+5\right)=30\)
\(3x+9=30\)
\(3x=30-9\)
\(3x=21\)
\(x=21\text{ : }3\)
\(x=7\)
\(\left(x+1\right)+\left(x+3\right)+\left(x+5\right)=30\)
\(x+1+x+3+x+5=30\)
\(\left(x+x+x\right)+\left(1+3+5\right)=30\)
\(3x+9=30\)
\(3x=30-9\)
\(3x=21\)
\(x=21\text{ : }3\)
\(x=7\)