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a.-1,75-(-\(\dfrac{1}{9}\)-2\(\dfrac{1}{8}\))
-1,75-\(\dfrac{1}{9}+\dfrac{17}{8}\)
\(-\dfrac{7}{4}-\dfrac{1}{9}+\dfrac{17}{8}\)
\(\dfrac{-126}{72}-\dfrac{8}{72}+\dfrac{153}{72}\)
=\(\dfrac{19}{72}\)
b.\(\dfrac{-1}{12}-\left(2\dfrac{5}{8}-\dfrac{1}{3}\right)\)
\(\dfrac{-1}{12}-\left(\dfrac{21}{8}-\dfrac{1}{3}\right)\)
\(\dfrac{-1}{12}-\dfrac{21}{8}+\dfrac{1}{3}\)
\(\dfrac{-2}{24}-\dfrac{63}{24}+\dfrac{64}{24}\)
=\(\dfrac{-1}{24}\)
d: \(\dfrac{1}{27}:\left(-\dfrac{1}{3}\right)^2+75\%\cdot\left(-\dfrac{2^2}{3}\right)\)
\(=\dfrac{1}{27}:\dfrac{1}{9}+\dfrac{3}{4}\cdot\dfrac{-4}{3}\)
\(=\dfrac{1}{3}-1\)
\(=-\dfrac{2}{3}\)
1: x=3/4-1/2=3/4-2/4=1/4
2: x-1/5=2/11
=>x=2/11+1/5=21/55
3: x-5/6=16/42-8/56
=>x-5/6=8/21-4/28=5/21
=>x=5/21+5/6=15/14
4: x/5=5/6-19/30
=>x/5=25/30-19/30=6/30=1/5
=>x=1
5: =>|x|=1/3+1/4=7/12
=>x=7/12 hoặc x=-7/12
6: x=-1/2+3/4
=>x=3/4-1/2=1/4
11: x-(-6/12)=9/48
=>x+1/2=3/16
=>x=3/16-1/2=-5/16
1)x= 1/4
2)x= 2/11+ 1/5
x= 21/55
3)x - 5/6 = 5/21
x = 5/21+5/6
x = 15/14
4)x/5 = 5/6 + -19/30
x:5 = 1/5
x = 1/5.5
x = 1
5) |x| - 1/4 = 6/18
|x| = 6/18 - 1/4
|x| =7/12
⇒x= 7/12 hoặc -7/12
6)x = -1/2 +3/4
x= 1/4
7) x/15 = 3/5 + -2/3
x:15 = -1/15
x = -1/15. 15
x = -1
8)11/8 + 13/6 = 85/x
85/24 = 85/x
⇒ x = 24
9) x - 7/8 = 13/12
x = 13/12 + 7/8
x = 47/24
10)x - -6/15 = 4/27
x = 4/27 + (-6/15)
x = -34/135
11) -(-6/12)+x = 9/48
x= 9/48 - 6/12
x = -5/16
12) x - 4/6 = 5/25 + -7/15
x -4/6 = -4/15
x = -4/15 + 4/6
x = 2/5
\(A=1-2+3-4+5-6+7-8+...+99-100\)
\(A=\left(-1\right)+\left(-1\right)+\left(-1\right)+\left(-1\right)+...+\left(-1\right)\)
\(A=\left(-1\right).50\)
\(A=-50\)
\(B=1+3-5-7+9+11-...-397-399\)
\(B=1-2+2-2+2-...+2-2-399\)
\(B=1-399\)
\(B=-398\)
\(C=1-2-3+4+5-6-7+...+97-98-99+100\)
\(C=-1+1-1+1-...-1+1\)
\(C=0\)
\(D=2^{2024}-2^{2023}-...-1\)
\(D=2^{2024}-\left(2^0+2^1+2^2+...2^{2023}\right)\)
\(D=2^{2024}-\left(\dfrac{2^{2024}-1}{2-1}\right)\)
\(D=2^{2024}-\left(2^{2024}-1\right)\)
\(D=2^{2024}-2^{2024}+1\)
\(D=1\)
A = 1 - 2 + 3 - 4 + 5 - 6 + 7 - 8 +...+ 99 - 100
A = (1 - 2) + ( 3 - 4) + ( 5- 6) +....+(99 - 100)
Xét dãy số 1; 3; 5;...;99
Dãy số trên là dãy số cách đều có khoảng cách là: 3 - 1 = 2
Dãy số trên có số số hạng là: (99 - 1) : 2 + 1 = 50 (số)
Vậy tổng A có 50 nhóm, mỗi nhóm có giá trị là: 1- 2 = -1
A = - 1\(\times\)50 = -50
b,
B = 1 + 3 - 5 - 7 + 9 + 11-...- 397 - 399
B = ( 1 + 3 - 5 - 7) + ( 9 + 11 - 13 - 15) + ...+( 393 + 395 - 397 - 399)
B = -8 + (-8) +...+ (-8)
Xét dãy số 1; 9; ...;393
Dãy số trên là dãy số cách đều có khoảng cách là: 9-1 = 8
Dãy số trên có số số hạng là: ( 393 - 1): 8 + 1 = 50 (số hạng)
Tổng B có 50 nhóm mỗi nhóm có giá trị là -8
B = -8 \(\times\) 50 = - 400
c,
C = 1 - 2 - 3 + 4 + 5 - 6 +...+ 97 - 98 - 99 +100
C = ( 1 - 2 - 3 + 4) + ( 5 - 6 - 7+ 8) +...+ ( 97 - 98 - 99 + 100)
C = 0 + 0 + 0 +...+0
C = 0
d, D = 22024 - 22023- ... +2 - 1
2D = 22005- 22004 + 22003+...- 2
2D + D = 22005 - 1
3D = 22005 - 1
D = (22005 - 1): 3
a.
\(\left(1\frac{1}{4}+\frac{3}{5}\right):\left(-\frac{11}{12}\right)+\left(\frac{3}{8}-1\frac{2}{5}\right):\left(-\frac{11}{12}\right)\)
\(=\left(\frac{5}{4}+\frac{3}{5}+\frac{3}{8}-\frac{7}{5}\right):\left(-\frac{11}{12}\right)\)
\(=\left(\frac{13}{8}-\frac{4}{5}\right):\left(-\frac{11}{12}\right)\)
\(=\frac{33}{40}:\left(-\frac{11}{12}\right)\)
\(=\frac{33}{40}\cdot\left(-\frac{12}{11}\right)\)
\(=\frac{-9}{10}\)
b.
\(\left(\frac{3}{8}-1\frac{2}{5}\right):\left(-\frac{11}{15}\right)+\left(1\frac{1}{4}+\frac{3}{5}\right):\left(-\frac{11}{15}\right)\)
\(=\left(\frac{3}{8}-\frac{7}{5}+\frac{5}{4}+\frac{3}{5}\right):\left(-\frac{11}{15}\right)\)
\(=\left(\frac{13}{8}-\frac{4}{5}\right):\left(-\frac{11}{15}\right)\)
\(=\frac{33}{40}:\left(-\frac{11}{15}\right)\)
\(=\frac{33}{40}\cdot\left(-\frac{15}{11}\right)\)
\(=\frac{-9}{8}\)
1. Tính hợp lí :
a) \(\frac{6}{7}.\frac{5}{11}+\frac{5}{7}.\frac{2}{11}-\frac{5}{7}.\frac{14}{11}\)
\(=\frac{5}{7}.\left(\frac{6}{11}+\frac{2}{11}-\frac{14}{11}\right)\)
\(=\frac{5}{7}.\frac{-6}{11}=-\frac{30}{77}\)
b) \(\frac{1}{3}.\frac{4}{5}+\frac{1}{3}.\frac{6}{5}-\frac{1}{3}\)
\(\frac{1}{3}.\left(\frac{4}{5}+\frac{6}{5}-\frac{1}{3}\right)\)
\(=\frac{1}{3}.\frac{5}{3}=\frac{5}{9}\)
1: \(B=75\%+1\dfrac{1}{5}\left(-1,25\right)+2\dfrac{1}{3}\)
\(=\dfrac{3}{4}+\dfrac{6}{5}\cdot\dfrac{-5}{4}+\dfrac{7}{3}\)
\(=\dfrac{3}{4}-\dfrac{6}{4}+\dfrac{7}{3}=\dfrac{7}{3}-\dfrac{3}{4}\)
\(=\dfrac{28}{12}-\dfrac{9}{12}=\dfrac{19}{12}\)
2: \(C=\left(\dfrac{2}{5}-\dfrac{5}{6}-\dfrac{2}{15}\right):\dfrac{8}{15}-\left(-\dfrac{1}{2}\right)^2\)
\(=\left(\dfrac{12}{30}-\dfrac{25}{30}-\dfrac{4}{30}\right)\cdot\dfrac{15}{8}-\dfrac{1}{4}\)
\(=\dfrac{-17}{30}\cdot\dfrac{15}{8}-\dfrac{1}{4}=\dfrac{-17}{16}-\dfrac{1}{4}=-\dfrac{17}{16}-\dfrac{4}{16}=-\dfrac{21}{16}\)
3: \(1\dfrac{5}{27}\cdot\left(-\dfrac{3}{2}\right)^2+\left(2,6-1\dfrac{3}{15}\right):\left(-\dfrac{3}{8}\right)\)
\(=\dfrac{32}{27}\cdot\dfrac{9}{4}+\left(2,6-1,2\right)\cdot\dfrac{-8}{3}\)
\(=\dfrac{8}{3}+1,4\cdot\dfrac{-8}{3}=\dfrac{8}{3}\cdot\left(1-1,4\right)=\dfrac{8}{3}\cdot\dfrac{-2}{5}=-\dfrac{16}{15}\)
4: \(A=\dfrac{3}{11}:\dfrac{4}{3}+\dfrac{8}{11}:\dfrac{4}{3}+\dfrac{1}{4}\)
\(=\left(\dfrac{3}{11}+\dfrac{8}{11}\right):\dfrac{4}{3}+\dfrac{1}{4}\)
\(=1:\dfrac{4}{3}+\dfrac{1}{4}=\dfrac{3}{4}+\dfrac{1}{4}=1\)
5: \(1\dfrac{13}{15}\cdot0,75-\left(\dfrac{11}{20}+25\%\right):\dfrac{8}{5}\)
\(=\dfrac{28}{15}\cdot\dfrac{3}{4}-\left(0,55+0,25\right)\cdot\dfrac{5}{8}\)
\(=\dfrac{7}{5}-0,8\cdot\dfrac{5}{8}=\dfrac{7}{5}-\dfrac{8}{10}\cdot\dfrac{5}{8}=\dfrac{7}{5}-\dfrac{5}{10}=\dfrac{14}{10}-\dfrac{5}{10}=\dfrac{9}{10}\)
1)B=3/4+6/5*(-5/4)+7/3
=3/4+-3/2+7/3
=-3/4+7/3
=19/12
Bạn cần gấp thì m gui c1 trc ah