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![](https://rs.olm.vn/images/avt/0.png?1311)
x + ( x + 1 ) + ( x + 2 ) + ( x + 3 ) + ..+ ( x + 99 ) = 5950
=> ( x + x + x +....+x) + ( 1 + 2 + 3+ ....+ 99) = 5950
Có tất cả số hạng ở dãy số tự nhiên là
( 99 -1) : 1 + 1 = 99 số
Tổng dãy số tự nhiên là
( 99 + 1) x 99 : 2 = 4950
Tổng dãy số x là
99 + 1=100 số x
x + ( x + 1 ) + ( x + 2 ) + ( x + 3 ) + ..+ ( x + 99 ) = 5950
hay 100x + 4950 = 5950
100x = 5950 - 4950
100x = 1000
x = 10
Vậy x =10
\(x+\left(x+1\right)+\left(x+2\right)+...+\left(x+99\right)=5950\)
\(x+x+1+x+2+...+x+99=5950\)
\(100x+\left(1+2+3+...+99\right)=5950\)
\(100x+\left(99+1\right).99:2=5950\)
\(100x+4950=5950\)
\(100x=5950-4950\)
100x=1000
x=10
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\left[x+1+x+2+x+3+...+x+100\right]=5950\)
\(\left[\left(x+x+x+...+x\right)+\left(1+2+3+4+...+100\right)\right]=5950\)
\(\left[\left(x+x+x+...+x\right)+\left(\frac{\left(100+1\right)\left[\left(100-1\right):1+1\right]}{2}\right)\right]=5950\)
\(\left[100x+5050\right]=5950\)
\(100x=900\Leftrightarrow x=9\)
![](https://rs.olm.vn/images/avt/0.png?1311)
#) Giải :
a) 6,62 x \(x\)+ 3,38 x \(x\)= 5
( 6,62 + 3,38 ) x \(x\) = 5
10 x \(x\) = 5
\(x\) = 5 : 10
\(x\) = 0,5
b) \(x\)x 0,5 + \(\frac{1}{4}\)x \(x\)= \(\frac{4}{5}\)x 3
\(x\)x 0,5 + \(\frac{1}{4}\)x \(x\) = \(\frac{12}{5}\)
\(x\)x ( 0,5 + \(\frac{1}{4}\)) = \(\frac{12}{5}\)
\(x\)x 0,75 = \(\frac{12}{5}\)
\(x\) = \(\frac{12}{5}\): 0,75
\(x\) = 3,2
![](https://rs.olm.vn/images/avt/0.png?1311)
a) \(15-3\left(x-1\right)-x=20\)
\(15-3x+3-x=20\)
\(-4x=2\)
\(x=-\frac{1}{2}\)
b) \(6x-2\left(x+3\right)=10\)
\(6x-2x-6=10\)
\(4x=16\)
\(x=4\)
c) \(25:\left(x+4\right)=5\)
\(x+4=25:5=5\)
\(x=1\)
d tự làm nha!
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{1}{7}\cdot\frac{2}{3}+\frac{5}{6}:\frac{3}{10}-\frac{2}{3}\cdot\frac{3}{7}\)
\(=\left(\frac{1}{7}\cdot\frac{2}{3}-\frac{2}{3}\cdot\frac{3}{7}\right)+\frac{5}{6}\cdot\frac{10}{3}\)
\(=\frac{2}{3}\cdot\left(-\frac{2}{7}\right)+\frac{5}{3}\cdot\frac{5}{3}\)
\(=-\frac{4}{21}+\frac{25}{6}=\frac{167}{42}\)
Xin lỗi không nhanh được
![](https://rs.olm.vn/images/avt/0.png?1311)
a. 8 x 37 x 5 x 25 = (8 x 25) x 37 x 5
= 200 x 5 x 37 = 1000 x 37 = 37000
b. 48 x 34 + 6 x 66 x 8 = 48 x 34 + 48 x 66 = 48 x ( 34 + 66) = 48 x 100 = 4800
c. 17 x (13 - 5) + 17 x 5 = 17 x 8 + 17 x 5 = 17 x (8 + 5) = 17 x 13 = 221
d. 78 x 100 - 100 = 78 x 100 - 100 x 1 = 100(78 - 1) = 100 x 77 = 7700
e. 6 x 17 x 8 + 3 x 37 x 16 + 4 x 46 x 12
= 48 x 17 + 48 x 37 + 48 x 46
= 48 x (17 + 37 + 46)
= 48 x 100 = 4800
f. 47 x 43 + 47 x 73 - 8 x 47 x 2 = 47 x 43 + 47 x 73 - 47 x 16 = 47 x (43 + 73 - 16) = 47 x 100 = 4700
8×37×5×25=296×5×25=1480×25=37000
48×34+6×66×8=1632+396×8=1632+3168=4800
15×(13-7)+17×5=15×6+17×5=90+85=175
78×100-100=7800-100=7700
![](https://rs.olm.vn/images/avt/0.png?1311)
\(\frac{10}{7}\cdot\frac{2}{3}+\frac{5}{6}:\frac{3}{10}-\frac{2}{3}\cdot\frac{3}{7}\)
\(=\left(\frac{10}{7}\cdot\frac{2}{3}-\frac{2}{3}\cdot\frac{3}{7}\right)+\frac{5}{6}\cdot\frac{10}{3}\)
\(=\frac{2}{3}\left(\frac{10}{7}-\frac{3}{7}\right)+\frac{5\cdot10}{6\cdot3}\)
\(=\frac{2}{3}\cdot1+\frac{25}{9}\)
\(=\frac{2}{3}+\frac{25}{9}\)
\(=\frac{31}{9}\)
\(x + ( x + 1 ) + ( x + 2 ) + ( x + 3 ) + ..+ ( x + 99 ) = 5950\)
\(100 x + ( 1 + 2 + 3 + ... + 99 ) = 5950\)
\(100 x + 4950 = 5950\)
\(100 x = 5950 − 4950\)
\(100 x = 1000\)
\(x = 1000 : 100\)
\(x=10\)
__________________________________________
\(1 + 2 + 3 + ... + 99\)
Số các số hạng :\(( 99 − 1 ) : 1 + 1 = 99\) (số hạng)
Tổng:\(( 1 + 99 ) × 99 : 2 = 4950\)
`#Yaa.`