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a) Ta có 1+2+3+4+...+x=210
=> x.(x-1):2=210
=>x.(x-1)=210.2=420=20.21
=>x=20
b) Ta có (x+1)+(x+2)+(x+3)+...+(x+99)=6138
=> x.99 +1+2+3+...+99=6138
=>x.99+4851=6138
=>x.99=6138-4851=1287
=>x=1287:99=13
OK
1. 1/2-(x-1/4)=1/3
=> x-1/4=1/2-1/3
=> x-1/4= 1/6
=> x= 1/6+1/4=5/12
2. 3/2*(x-1/2-1)=5/4
=> x-1/2-1=5/4:3/2
=> x-1/2= 5/6+1
=> x = 11/6+1/2
=> x= 7/3
3. 11/2-9/2*(x-3/4)=1
=> 9/2*(x-3/4)= 11/2-1
=> x-3/4 = 9/2:9/2
=> x= 1+3/4
=> x= 7/4
Chúc bạn Hk tốt!!!!!
1. x=\(\frac{5}{12}\)
2. x=\(\frac{7}{3}\)
3. x= \(\frac{7}{4}\)
Chúc bạn Hk tốt!!!
\(\frac{3}{4}:x=\frac{1}{2}-\frac{4}{5}\)
ĐẾN ĐÂY LÀ SAI ĐỀ RÔI
\(\frac{4}{5}+\frac{3}{4}:x=\frac{1}{2}\)
\(\frac{3}{4}:x=\frac{1}{2}-\frac{4}{5}=-\frac{3}{10}\)
\(x=\frac{3}{4}:\frac{-3}{10}=-\frac{5}{2}\)
a) \(x.\frac{3}{4}=\frac{4}{5}.2\)
\(x.\frac{3}{4}=\frac{8}{5}\)
\(x=\frac{8}{5}:\frac{3}{4}=\frac{32}{15}\)
b) \(x:1\frac{1}{7}=2\frac{2}{3}\)
\(x:\frac{8}{7}=\frac{8}{3}\)
\(x=\frac{8}{3}.\frac{8}{7}=\frac{64}{21}\)
c) \(x-1\frac{2}{5}=4\frac{1}{6}-2\frac{2}{3}\)
\(x-\frac{7}{5}=\frac{25}{6}-\frac{8}{3}=\frac{3}{2}\)
\(x=\frac{3}{2}+\frac{7}{5}=\frac{29}{10}\)
d) \(2\frac{2}{3}+x:\frac{3}{2}=2\frac{1}{3}\)
\(\frac{8}{3}+x:\frac{3}{2}=\frac{7}{3}\)vô lí vì 8/3 lớn hơn 7/3
\(\left(x+\frac{1}{2}\right)+\left(x+\frac{1}{4}\right)+\left(x+\frac{1}{8}\right)+\left(x+\frac{1}{16}\right)=1\)
\(x+x+x+x+\left(\frac{1}{2}+\frac{1}{4}+\frac{1}{8}+\frac{1}{16}\right)=1\)
\(4x+\frac{15}{16}=1\)
\(4x=1-\frac{15}{16}\)
\(4x=\frac{1}{16}\)
\(x=\frac{1}{16}\div4\)
\(x=\frac{1}{64}\)
ta coi x để ra mội bên ta có 1/2 + 1/4 + 1/8 + 1/6 = 25/24
x + 25/24 = 1
x = 1 - 25/24
x = -1/24
mk nha
a, (x-3).2=4
x-3 = 2
x = 5
b, 3/2 - 2/3 : x = 1/2
2/3 : x = 3/2 - 1/2
2/3 : x = 1
x = 3/2
c, 4/3 + 1/3 : (x - 1/2) = 4
1/3 : (x - 1/2) = 4 - 4/3
1/3 : (x - 1/2) = 8/3
x - 1/2 = 1/8
x = 9/8
a)\(\frac{3}{5}+25-\frac{1}{5}=\frac{3}{5}-\frac{1}{5}+25=\frac{2}{5}+25=25\frac{2}{5}=\frac{129}{5}\)
b)\(6h45+14h30:5=6,75h+14,5h:5=6,75h+2,9h=9,65h\)
c)\(13.3.32,37+67,63.39=39.32,37+67,63.39=39.\left(32,37+67,63\right)=39.100=3900\)
d)
a.\(\frac{3}{5}+25-\frac{1}{5}=\left(\frac{3}{5}-\frac{1}{5}\right)+25=\frac{2}{5}+25=25.4\)
b. 6h45' + 14h30' : 5 = 6h45' + 2h54' = 9h 39'
c.13 x 3 x 32.5 + 67.63 x 39 = 3905.07
d.\(\left(1-\frac{1}{2}\right)\cdot\left(1-\frac{1}{3}\right)\cdot\left(1-\frac{1}{5}\right)\)
=\(\left(\frac{2}{2}-\frac{1}{2}\right)\cdot\left(\frac{3}{3}-\frac{1}{3}\right)\cdot\left(\frac{4}{4}-\frac{1}{4}\right)\)
=\(\frac{1}{2}\cdot\frac{2}{3}\cdot\frac{3}{4}=\frac{1}{4}\)
b.(x+1)+(x+2)+...+(x+99)=6138
(x+x+..+x)+(1+2+...+99)=6138
99 x X + a=6138
99 x X=6138 - a
x=(6138- a):99
x=b
a;b là kết quả bn tự tính nha!:>
a) 1 + 2 + 3 + 4 + ....+ x = 210
=> ( x + 1 ) . x : 2 = 210
=> ( x + 1 ) . x = 420
=> ( x + 1 ) . x = 20 x 21
=> x = 20
b) ( x + 1 ) + ( x + 2 ) + ( x + 3 ) + ....+ ( x + 99 ) = 6138
=> ( x + x + x + .... + x ) + ( 1 + 2 + 3 + .... + 99 ) = 6138
=> 99x + ( 1 + 2 + 3 + ...+ 99 ) = 6138
Ta có :
Số số hạng là : ( 99 - 1 ) + 1 = 99
Tổng là : ( 99 + 1 ) . 99 : 2 = 4950
=> 99x + 4950 = 6138
=> 99x = 1188
=> x = 12