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f) \(2\cdot5^2+3:71^0-54:3^3\)
\(=2\cdot25+3:1-54:27\)
\(=50+3-2\)
\(=51\)
h) \(5\cdot3^2-32:4^2\)
\(=5\cdot9-32:16\)
\(=45-2\)
\(=43\)
k) \(5^6:5^4+2^3\cdot2^2-1^{2017}\)
\(=5^2+2^5-1\)
\(=25+32-1\)
\(=56\)
n) \(23\cdot75+5^2\cdot10+5^2\cdot13+180\)
\(=23\cdot25\cdot3+25\cdot10+25\cdot13+180\)
\(=25\cdot\left(23\cdot3+10+13\right)+180\)
\(=25\cdot92+180\)
\(=2300+180\)
\(=2480\)
f: =2*25+3-54:27
=50+3-2
=51
h: =5*9-32:16
=45-2=43
k: =5^2+2^5-1
=25+32-1
=25+31=56
n: =23*75+25*23+180
=2300+180
=2480
`1+1/3=4/3`
`=>1/(1+1/3)=1:4/3=3/4`
`=>B=(1-1/3+3/4)/(1-1/3-3/4)`
`=(2/3+3/4)/(2/3-3/4)`
`=17/12:(-1/12)`
`=-17`
\(\frac{3}{5}.\left(\frac{5}{3}-\frac{2}{7}\right)-\left(\frac{7}{3}-\frac{3}{7}\right).\frac{3}{5}\)
\(=\frac{3}{5}.\text{[}\left(\frac{5}{3}-\frac{2}{7}\right)-\left(\frac{7}{3}-\frac{3}{7}\right)\text{]}\)
\(=\frac{3}{5}.\text{[}\frac{5}{3}-\frac{2}{7}-\frac{7}{3}+\frac{3}{7}\text{]}\)
\(=\frac{3}{5}.\text{[}\left(\frac{5}{3}-\frac{7}{3}\right)-\left(\frac{2}{7}-\frac{3}{7}\right)\text{]}\)
\(=\frac{3}{5}.\text{[}\frac{-2}{3}-\frac{-1}{7}\text{]}\)
\(=\frac{3}{5}.\left(\frac{-2}{3}+\frac{1}{7}\right)\)
\(=\frac{3}{5}.\left(\frac{-14}{21}+\frac{3}{21}\right)\)
\(=\frac{3}{5}.\frac{-11}{21}\)
\(=\frac{3.\left(-11\right)}{5.21}\)
\(=\frac{-11}{5.7}=\frac{-11}{35}\)
Chúc bạn học tốt
\(Xét A = 1/(4.9)+1/(9.14)+1/(14.19)+...+1/(44.49)
-> 5A = 5/(4.9) + 5/(9.14) + 5/(14.19) + ... + 5/(44.49)
= 1/4 - 1/9 + 1/9 - 1/14 + 1/14 - 1/19 + ... + 1/44 - 1/49
= 1/4 - 1/49 = 45/196 -> A = 9 / 196
Xét B = (−1−3−5−7−...−49)/89
= (1 + 3 + 5 + ... + 49) / -89
= 625 / -89
biểu thức đầu bài có giá trị: A.B = 9/196 * 625/-89 = - 5625 / 17444\)Xét A = 1/(4.9)+1/(9.14)+1/(14.19)+...+1/(44.49)
-> 5A = 5/(4.9) + 5/(9.14) + 5/(14.19) + ... + 5/(44.49)
= 1/4 - 1/9 + 1/9 - 1/14 + 1/14 - 1/19 + ... + 1/44 - 1/49
= 1/4 - 1/49 = 45/196 -> A = 9 / 196
Xét B = (−1−3−5−7−...−49)/89
= (1 + 3 + 5 + ... + 49) / -89
= 625 / -89
biểu thức đầu bài có giá trị: A.B = 9/196 * 625/-89 = - 5625 / 17444
tick nha
Câu 3:
a: Số học sinh của lớp là:
4+15+20+10+1=50 bạn
\(\%Xs=\dfrac{4}{50}=8\%\)
%Tốt=15/50=30%
%Khá=20/50=40%
%Đạt=10/50=20%
%Chưa đạt=1/50=2%
b:
\(\frac{\left(-3\right)^2.3^2.32}{3^4.\left(-2\right)^6}=\frac{3^4.2^5}{3^4.2^6}=\frac{1}{2}\)
\(B=\frac{1-\frac{1}{3}+\frac{1}{1+\frac{1}{3}}}{1-\frac{1}{3}-\frac{1}{1+\frac{1}{3}}}\)
\(B=\frac{\frac{2}{3}+\frac{1}{\frac{2}{3}}}{\frac{2}{3}-\frac{1}{\frac{2}{3}}}\)
\(B=\frac{\frac{2}{3}+\frac{3}{2}}{\frac{2}{3}-\frac{3}{2}}\)
\(B=\frac{\frac{13}{6}}{\frac{-5}{6}}\)
\(B=\frac{13}{6}:\frac{-5}{6}\)
\(B=\frac{-13}{5}\)