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a: \(A=\dfrac{2}{3}-4\cdot\dfrac{5}{4}=\dfrac{2}{3}-5=-\dfrac{13}{3}\)
b: \(B=\dfrac{-2+5}{6}\cdot11-7=\dfrac{11}{2}-7=-\dfrac{3}{2}\)
c: \(=1+\dfrac{2}{3}\cdot\dfrac{1}{2}+\dfrac{27}{4}+5-1\)
\(=\dfrac{1}{3}+\dfrac{27}{4}+5=\dfrac{145}{12}\)
d: \(D=\dfrac{2}{3}\cdot\dfrac{2}{5}-\dfrac{1}{5}\cdot\dfrac{1}{6}=\dfrac{4}{15}-\dfrac{1}{30}=\dfrac{7}{30}\)
a) \(2^3.3^2=8.9=72\)
b) \(5^{10}:5^7=5^2=25\)
c) \(2^6:2=2^5=32\)
d) \(7^4:7^4=7^0=1\)
e) \(9^5:9^5=9^0=1\)
a/ A= 1-3+5-7+9-11+......+97-99
= -2+(-2)+(-2)+......+(-2)
= (-2).25=-50
b/B=-1-2-3-4-...-100
=-(1+2+3+4+...+100)
=-5050
c/C=1-2+3-4+5-6+......+99-100
= -1+(-1)+(-1)+.............+(-1)
=(-1).50=-50
d/D=1-2-3+4+5-6-7+8+9-....+94-95
= (1-2-3+4)+(5-6-7+8)+.......+(92-93-94+95)
= 0+0+0+...+0=0
Câu 1 :
a, 8.( -5 ).( -4 ).2
= [ 8.2 ].[( -5 ).(-4 ]
= 16.20
= 320
b, \(1\frac{3}{7}+\frac{-1}{3}+2\frac{4}{7}\)
\(=\frac{10}{7}+\frac{-1}{3}+\frac{18}{7}\)
\(=\frac{11}{3}\)
c, \(\frac{8}{5}.\frac{2}{3}+\frac{-5.5}{3.5}\)
\(=\frac{8}{3}+\frac{-5}{3}\)
\(=\frac{3}{3}=1\)
d, \(\frac{6}{7}+\frac{5}{8}:5-\frac{3}{16}.\left(-2\right)^2\)
\(=\frac{6}{7}+\frac{1}{8}-\frac{3}{16}.4\)
\(=\frac{55}{56}-\frac{3}{4}\)
\(=\frac{13}{56}\)
Câu 2 :
a, 2x + 10 = 16
2x = 16 + 10
2x = 26
x = 26 : 2
x = 13
b, \(x-\frac{1}{3}=\frac{5}{4}\)
\(x=\frac{5}{4}+\frac{1}{3}\)
\(x=\frac{19}{12}\)
c, \(2x+3\frac{1}{3}=7\frac{1}{3}\)
\(2x+\frac{10}{3}=\frac{22}{3}\)
\(2x=\frac{22}{3}-\frac{10}{3}\)
\(2x=4\)
\(x=4:2\)
\(x=2\)
d, \(\left(\frac{2}{11}+\frac{1}{3}\right)x=\left(\frac{1}{7}-\frac{1}{8}\right).56\)
\(\frac{17}{33}x=1\)
\(x=1-\frac{17}{33}\)
\(x=\frac{16}{33}\)
\(A=2^5.5^2-8^2-7=800-64-7=729=27^2\)
\(B=2^3.4^2+3^2.3^2-40=128+81-40=169=13^2\)
\(C=11.2^4+6^2.19+40=176+684+40=900=30^2\)
\(D=4^3+6^3+7^3+2=64+216+343+2=625=25^2\)
a ) A = 2 10 - 2 5 = 1024 - 32 = 992 . b ) B = 4 3 - 4 2 - 4 = 64 - 16 - 4 = 44 . c ) C = 3 2 . 2 3 + 4 3 . 2 5 = 9 . 8 + 64 . 32 = 2120 . d ) D = 1 3 + 2 3 + 3 3 + 4 3 + 5 3 = 1 + 8 + 27 + 64 + 125 = 225 .