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a) \(\dfrac{3}{7}-\dfrac{4}{11}-\dfrac{3}{7}\)
=\(\left(\dfrac{3}{7}-\dfrac{3}{7}\right)-\dfrac{4}{11}\)
\(=-\dfrac{4}{11}\)
b) \(-\dfrac{5}{11}+\dfrac{3}{8}-\dfrac{6}{11}\)
\(=\left(-\dfrac{5}{11}-\dfrac{6}{11}\right)+\dfrac{3}{8}\)
\(=-1+\dfrac{3}{8}=-\dfrac{8}{8}+\dfrac{3}{8}=-\dfrac{5}{8}\)
c) \(\dfrac{3}{4}-\dfrac{1}{3}-\dfrac{11}{4}\)
\(=\left(\dfrac{3}{4}-\dfrac{11}{4}\right)-\dfrac{1}{3}\)
\(=-2-\dfrac{1}{3}=-\dfrac{6}{3}-\dfrac{1}{3}=-\dfrac{7}{3}\)
a) \(\dfrac{-5}{9}-\dfrac{4}{15}+\dfrac{2}{9}-\dfrac{11}{15}\)
\(=\left(\dfrac{-5}{9}+\dfrac{2}{9}\right)-\left(\dfrac{4}{15}+\dfrac{11}{15}\right)\)
\(=\dfrac{-3}{9}-\dfrac{15}{15}\)
\(=-\dfrac{1}{3}-1\)
\(=-\dfrac{4}{3}\)
b) \(\dfrac{-8}{13}-\dfrac{7}{16}+\dfrac{21}{13}-\dfrac{1}{6}\)
\(=\left(\dfrac{-8}{13}+\dfrac{21}{13}\right)-\dfrac{7}{16}-\dfrac{1}{6}\)
\(=\dfrac{13}{13}-\dfrac{29}{48}\)
\(=1-\dfrac{29}{48}\)
\(=\dfrac{19}{48}\)
c) \(\dfrac{-15}{25}-\dfrac{14}{21}+\dfrac{8}{5}-\dfrac{5}{3}\)
\(=\dfrac{-3}{5}-\dfrac{2}{3}+\dfrac{8}{5}-\dfrac{5}{3}\)
\(=\left(\dfrac{-3}{5}+\dfrac{8}{5}\right)-\left(\dfrac{2}{3}+\dfrac{5}{3}\right)\)
\(=\dfrac{5}{5}-\dfrac{7}{3}\)
\(=1-\dfrac{7}{3}\)
\(=-\dfrac{4}{3}\)
a: =-5/9+2/9-11/15-4/15
=-3/9-1
=-12/9=-4/3
b: =-8/13+21/13-7/16-1/6
=1-1/6-7/16
=5/6-7/16
=19/48
c: =-15/25+8/5-2/3-5/3
=-7/3+1
=-4/3
Bn tham khảo
Bài 1 :
a) \(...=5^5:5^4=5\)
b) \(...=7^8:7^9=\dfrac{1}{7}\)
c) \(...=2^{15}:\left(2^6.2^5\right)=2^{15}:2^{11}=2^4=16\)
d) \(...=3^{28}:3^{26}=3^2=9\)
Bài 2 :
a) \(...=3^2.3^3:3^4=3^5:3^4=3\)
b) \(...=10^9-10^9=0\)
c) \(...=5^{10}.5^{30}:5^{12}=5^{40}:5^{12}=5^{28}\)
Đổi:40%=2/5
Số Hsg là:35*1/7=5(HS)
Số Hs còn lại là:35-5=30(Hs)
Số Hs khá là:30*2/5=12(Hs)
Số Hs TB là:30-12=18(Hs)
Vậy số Hs TB là 18
Bài giải
Sử dụng công thức tính tổng dãy sô có quy luật của lớp 6, ta có:
12 + 22 + 32 + 42 +...+ 20082
= \(\frac{2008\left(2008^2+1\right)}{2}\)
= 4048193260
a) \(y+2\frac{3}{4}=5\frac{2}{3}\)
\(y+\frac{11}{4}=\frac{17}{3}\)
y = 35/12
b) \(y-1\frac{4}{5}=3\frac{2}{7}\)
y - 9/5 = 23/7
y = 178/35
\(a,y+2\frac{3}{4}=5\frac{2}{3}\)
\(\Rightarrow y+\frac{11}{4}=\frac{17}{3}\)
\(\Rightarrow y=\frac{17}{3}-\frac{11}{4}\)
\(\Rightarrow y=\frac{35}{12}\)
\(b,y-1\frac{4}{5}=3\frac{2}{7}\)
\(\Rightarrow y=3\frac{2}{7}-1\frac{4}{5}\)
\(\Rightarrow y=\frac{52}{35}\)
A = \(\frac{2}{3}+\left(\frac{5}{7}+\frac{-2}{3}\right)\)
= \(\frac{2}{3}+\frac{1}{21}\)
= \(\frac{5}{7}\)
hok thêm ak?