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BÀI 1
a, \(5\times\frac{-7}{10}=\frac{-35}{10}=\frac{-7}{2}\)
b, \(\frac{4}{5}\times\frac{-7}{10}=\frac{-28}{50}=\frac{-14}{25}\)
c, \(\frac{4}{9}+\frac{4}{3}\times\frac{16}{4}=\frac{4}{9}+\frac{16}{3}=\frac{52}{9}\)
d, \(\frac{11}{22}-\frac{3}{9}\times\frac{14}{21}=\frac{11}{22}-\frac{2}{9}=\frac{55}{198}=\frac{5}{18}\)
BÀI 2
\(A=\frac{6}{13}\times\frac{5}{7}+\frac{6}{13}\times\frac{2}{7}+\frac{17}{13}\)
\(A=\frac{30}{91}+\frac{12}{91}+\frac{17}{13}\)
\(A=\frac{30}{91}+\frac{12}{91}+\frac{119}{91}\)
\(A=\frac{161}{91}=\frac{23}{13}\)
\(B=\frac{11}{15}\times\frac{4}{11}+\frac{11}{15}\times\frac{5}{11}+\frac{11}{15}\times\frac{2}{11}\)
\(B=\frac{4}{15}+\frac{1}{3}+\frac{2}{15}\)
\(B=\frac{11}{15}\)
\(C=\left(\frac{19}{64}-\frac{33}{22}+\frac{24}{51}\right)\times\left(\frac{1}{5}-\frac{1}{15}-\frac{2}{15}\right)\)
\(C=\frac{-797}{1088}\times0\)
\(C=0\)
\(D=\frac{8}{13}\times\frac{7}{12}+\frac{8}{13}\times\frac{5}{12}-\frac{1}{12}\)
\(D=\frac{14}{39}+\frac{10}{39}-\frac{1}{12}\)
\(D=\frac{83}{156}\)
bạn biết câu náy không (24 + 11) . {546 - [14 . (64 - 2^{3}3) : 2]} =
\(C=\frac{4}{9.11.13}+\frac{4}{11.13.15}+...+\frac{4}{59.61.63}\)
\(=2\left(\frac{2}{9.11.13}+\frac{2}{11.13.15}+...+\frac{2}{59.61.63}\right)\)
\(=2\left(\frac{1}{9.11}-\frac{1}{11.13}+\frac{1}{11.13}-\frac{1}{13.15}+...+\frac{1}{59.61}-\frac{1}{61.63}\right)\)
\(=2\left(\frac{1}{9.11}-\frac{1}{61.63}\right)\)
\(=2.\frac{416}{42273}\)
\(=\frac{832}{42273}\)
a: =35/17-18/17-9/5+4/5
=1-1=0
b: =-7/19(3/17+8/11-1)
=7/19*18/187=126/3553
c: =26/15-11/15-17/3-6/13
=1-6/13-17/3
=7/13-17/3=-200/39
\(1+2+3+...+n=\frac{n\left(n+1\right)}{2}\)
\(1+3+5+7+...+\left(2n-1\right)=n^2\)
\(2+4+6+8+...+2n=n\left(n+1\right)\)
B = 1/4 x( 4/ 1x3x5 +4 /3x5x7 +...+ 4/47x49x51)
= 1/4 x( 1/ 1x3 - 1/3x5 +1/3x5 -1/5x7 +...+ 1/47x49 -1/49x51)
= 1/4 x( 1/1x3 -1/49x51)
= 1/4 x( 1/3 - 1/2499)
= 1/4 x 832/2499
= 208 /2499
Vậy B= 208 /2499
C= 1/ 9x11 -1/ 11x13 +1/ 11x13 -1/ 13x15 +... + 1/ 59x61 -1/61x63
= 1/ 9x11 -1/ 61x63
= 1/99 -1/3843
= 416 /42273
Vậy C= 416 /42273
Mình ko hieu ý thu 2