\(\frac{10}{17}-\frac{5}{13}-\frac{-7}{17}-\frac{8}{13}+\frac{11}{25}\)
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=10/17+-5/13+7/17+-8/13+-11/25
=1+-1+-11/25
=11/25
b ,
= 1+-2+3+-4+5+-6+......2011+-2012
=1+1+1+1+1.........+-2012
=1.2011+-2012
=2011+-2012
=-1
2.
2/3-x = 5/4
=>x=2/3-5/4
=>x=-7/12
b,
[124-(20-4x)]:30+7=11
=>124-(20-4x)] :30 =11-7
=>[124-(20-4x)]:30=4
=>124-(20-4x)=4x30
=>124-(20-4x)=120
=>20-4x=120-124
=>20-4x=4
=>4x=20-4
=>4x=16
=>x=16:4
=>x=4
bài 1
a, ghép cặp phân số 10/17 + 7/17 và 5/13 + -8/13
b, 1-2+3-4+5-6+.....+2011-2012
= ( 1-2) + ( 3-4) + ( 5-6) +....+(2011-2012)
= (-1) + (-1) + (-1) + ....+ (-1)
< từ 1 đến 2012 có 2012 số số hạng, suy ra có 1006 cặp mà mỗi cặp có giá trị = (-1) Suy ra tổng trên = (-1) * 1006=-1006
a) \(\frac{10}{17}-\frac{5}{13}+\frac{7}{17}+\frac{-8}{13}-\frac{11}{25}\)
\(=\frac{10}{17}+\frac{-5}{13}+\frac{7}{17}+\frac{-8}{13}+\frac{-11}{25}\)
\(=\left(\frac{10}{17}+\frac{7}{17}\right)+\left(\frac{-5}{13}+\frac{-8}{13}\right)+\frac{-11}{25}\)
\(=1+\left(-1\right)+\frac{-11}{25}\)
\(=0+\frac{-11}{25}\)
\(=\frac{-11}{25}\)
a) \(\frac{10}{17}-\frac{5}{13}+\frac{7}{17}+\frac{-8}{13}-\frac{11}{25}\)
\(=\frac{10}{17}+\frac{-5}{13}+\frac{7}{17}+\frac{-8}{13}+\frac{-11}{15}\)
\(=\left(\frac{10}{17}+\frac{7}{17}\right)+\left(\frac{-5}{13}+\frac{-8}{13}\right)+\frac{-11}{15}\)
\(=1+\left(-1\right)+\frac{-11}{15}\)
\(=0+\frac{-11}{15}\)
\(=\frac{-11}{15}\)
b) 1 - 2 + 3 - 4 + ...... + 2011 - 2012 ( có 2012 số )
= ( 1 - 2 ) + ( 3 - 4 ) + ....... + ( 2011 - 2012 ) ( có 1006 nhóm )
= ( - 1 ) + ( - 1 ) + ........ + ( - 1 ) ( có 1006 số )
= ( - 1 ) . 1006
= - 1006
\(\text{a)}A=\frac{9}{11}+\frac{5}{7}-\frac{20}{11}+\frac{8}{13}+\frac{2}{7}\)
\(A=\frac{9}{11}+\frac{5}{7}+\frac{-20}{11}+\frac{8}{13}+\frac{2}{7}\)
\(A=\left(\frac{9}{11}+\frac{-20}{11}\right)+\left(\frac{5}{7}+\frac{2}{7}\right)+\frac{8}{13}\)
\(A=\frac{-11}{11}+\frac{7}{7}+\frac{8}{13}\)
\(A=\left[\left(-1\right)+1\right]+\frac{8}{13}\)
\(A=0+\frac{8}{13}=\frac{8}{13}\)
\(\text{b)}B=\frac{8}{13}+\frac{9}{-17}+\frac{-34}{13}+\frac{-8}{17}\)
\(B=\left(\frac{8}{13}+\frac{-34}{13}\right)+\left(\frac{-9}{17}+\frac{-8}{17}\right)\)
\(B=\frac{-26}{13}+\left(-1\right)\)
\(B=\left(-2\right)+\left(-1\right)=-3\)
\(\text{Hok tốt!}\)
\(\text{@Kaito Kid}\)
a) \(\frac{-77}{143}+\frac{65}{143}-\frac{66}{143}+\frac{7}{22}\)
= \(\frac{-78}{143}+\frac{7}{22}\)= \(\frac{-6}{11}+\frac{7}{22}\)= \(\frac{-12}{22}+\frac{7}{22}\)
= \(\frac{-5}{22}\)
b) \(\frac{-4}{5}-\frac{20}{170}+\frac{51}{170}+\frac{150}{170}\)= \(\frac{-4}{5}-\frac{221}{170}\)
\(\frac{-4}{5}-\frac{13}{10}\)= \(\frac{-8}{10}-\frac{13}{10}\)=\(\frac{-21}{10}\)
a) \(\frac{31}{17}+\frac{-5}{13}+\frac{-8}{13}-\frac{14}{17}\)
\(=\left(\frac{31}{17}-\frac{14}{17}\right)+\left(\frac{-5}{13}+\frac{-8}{13}\right)\)
\(=1+\left(-1\right)\)
\(=0\)
b) \(\frac{-5}{7}.\frac{2}{11}+\frac{-5}{7}.\frac{9}{11}+\frac{5}{7}\)
\(=\frac{-5}{7}.\left(\frac{2}{11}+\frac{9}{11}\right)+\frac{5}{7}\)
\(=\frac{-5}{7}.1+\frac{5}{7}\)
\(=\frac{-5}{7}+\frac{5}{7}\)
\(=0\)
\(\dfrac{10}{17}-\dfrac{5}{13}-\dfrac{-7}{17}-\dfrac{8}{13}+\dfrac{11}{25}\)
\(=\left(\dfrac{10}{17}+\dfrac{7}{17}\right)-\left(\dfrac{5}{13}+\dfrac{8}{13}\right)+\dfrac{11}{25}\)
\(=1-1+\dfrac{11}{25}=\dfrac{11}{25}\)