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Bài 4:
a; \(\dfrac{1}{4}\) - \(\dfrac{1}{5}\) = \(\dfrac{5}{20}\) - \(\dfrac{4}{20}\) = \(\dfrac{1}{20}\)
b; \(\dfrac{3}{5}\) - \(\dfrac{-1}{2}\) = \(\dfrac{6}{10}\) + \(\dfrac{5}{10}\) = \(\dfrac{11}{10}\)
c; \(\dfrac{3}{5}\) - \(\dfrac{-1}{3}\) = \(\dfrac{9}{15}\) + \(\dfrac{5}{15}\) = \(\dfrac{14}{15}\)
d; \(\dfrac{-5}{7}\) - \(\dfrac{1}{3}\)= \(\dfrac{-15}{21}\) - \(\dfrac{7}{21}\)= \(\dfrac{-22}{21}\)
Bài 5
a; 1 + \(\dfrac{3}{4}\) = \(\dfrac{4}{4}\) + \(\dfrac{3}{4}\) = \(\dfrac{7}{4}\) b; 1 - \(\dfrac{1}{2}\) = \(\dfrac{2}{2}\) - \(\dfrac{1}{2}\) = \(\dfrac{1}{2}\)
c; \(\dfrac{1}{5}\) - 2 = \(\dfrac{1}{5}\) - \(\dfrac{10}{5}\) = \(\dfrac{-9}{5}\) d; -5 - \(\dfrac{1}{6}\) = \(\dfrac{-30}{6}\) - \(\dfrac{1}{6}\) = \(\dfrac{-31}{6}\)
e; - 3 - \(\dfrac{2}{7}\)= \(\dfrac{-21}{7}\) - \(\dfrac{2}{7}\)= \(\dfrac{-23}{7}\) f; - 3 + \(\dfrac{2}{5}\) = \(\dfrac{-15}{5}\) + \(\dfrac{2}{5}\)= - \(\dfrac{13}{5}\)
g; - 3 - \(\dfrac{2}{3}\) = \(\dfrac{-9}{3}\) - \(\dfrac{2}{3}\) = \(\dfrac{-11}{3}\) h; - 4 - \(\dfrac{-5}{7}\) = \(\dfrac{-28}{7}\)+ \(\dfrac{5}{7}\) = - \(\dfrac{23}{7}\)
Có quá nhiều bài, thứ nhất em đăng tách ra, thứ hai chụp gần cận cho rõ, thứ ba em chỉ đăng bài cần giúp
Bài 3:
a; \(\frac56-\frac89\) = \(\frac{15}{18}-\) \(\frac{16}{18}\) = - \(\frac{1}{18}\)
d; \(\frac{5}{16}-\frac{5}{24}\)
= \(\frac{15}{48}\) - \(\frac{10}{48}\)
= \(\frac{5}{48}\)
e; - \(\frac{7}{30}\) + \(\frac{8}{45}\)
= \(-\frac{21}{90}\) + \(\frac{16}{90}\)
= - \(\frac{5}{90}\)
= - \(\frac{1}{18}\)
f; \(\frac{7}{12}-\frac{-9}{20}\)
= \(\frac{35}{60}\) + \(\frac{27}{60}\)
= \(\frac{62}{60}\)
= 31/30
h; - \(\frac48\) + \(-\frac{3}{10}\)
= -\(\frac{20}{40}-\frac{12}{40}\)
= - \(\frac{32}{40}\)
= - \(\frac45\)
\(a,MSC:180\\ Có:-5=\dfrac{-5.180}{180}=\dfrac{-900}{180};\dfrac{17}{-20}=\dfrac{17.\left(-9\right)}{\left(-9\right).\left(-20\right)}=\dfrac{-153}{180};\dfrac{-16}{9}=\dfrac{-16.20}{9.20}=\dfrac{-320}{180}\\ ---\\ b.MSC:75\\ Có:\dfrac{13}{-15}=\dfrac{13.\left(-5\right)}{\left(-15\right).\left(-5\right)}=\dfrac{-65}{75};\dfrac{-18}{25}=\dfrac{-18.3}{25.3}=\dfrac{-54}{75};-3=\dfrac{-3.75}{75}=\dfrac{-225}{75}\)
| Phân số | Đọc | Tử Số | Mẫu số |
| \(\dfrac{5}{7}\) | Năm phần bẩy | 5 | 7 |
| \(\dfrac{-6}{11}\) | âm sáu phần mười một | -6 | 11 |
| \(\dfrac{-2}{13}\) | âm hai phần ba | -2 | 13 |
| \(\dfrac{9}{-11}\) | chín phần âm mười một | 9 | -11 |
a) 3h 20ph = 3 và 1/3 = 10/3
b) 1h 45 ph = 1 và 3/4 = 7/4
c) 2h 40 ph = 2 và 2/3 = 8/3
\(a,-\dfrac{9}{4}< 0;\dfrac{1}{3}>0.Nên:-\dfrac{9}{4}< \dfrac{1}{3}\\ b,-\dfrac{8}{3}< -2;\dfrac{4}{-7}>-1.Nên:-\dfrac{8}{3}< -2< -1< \dfrac{4}{-7}\\ Vậy:-\dfrac{8}{3}< \dfrac{4}{-7}\\ c,\dfrac{9}{-5}< -1;\dfrac{7}{-10}>-1.Nên:\dfrac{9}{-5}< -1< \dfrac{7}{-10}.Vậy:\dfrac{9}{-5}< \dfrac{7}{-10}\\ d,\dfrac{3}{14}>0;-\dfrac{6}{14}< 0.Nên:\dfrac{3}{14}>0>-\dfrac{6}{14}.Vậy:\dfrac{3}{14}>-\dfrac{6}{14}\\ e,\dfrac{7}{-12}=\dfrac{7.3}{-12.3}=\dfrac{21}{-36};\dfrac{11}{-18}=\dfrac{11.2}{-18.2}=\dfrac{22}{-36}\\ Vì:\dfrac{21}{-36}>\dfrac{22}{-36}.Nên:\dfrac{7}{-12}>\dfrac{11}{-18}\)
\(f,-\dfrac{4}{7}< -\dfrac{1}{2};-\dfrac{4}{10}>\dfrac{-1}{2}.Nên:-\dfrac{4}{7}< -\dfrac{1}{2}< -\dfrac{4}{10}.Vậy:-\dfrac{4}{7}< -\dfrac{4}{10}\\ g,-\dfrac{8}{15}< -\dfrac{1}{2};\dfrac{5}{-24}>-\dfrac{1}{2}.Nên:-\dfrac{8}{15}< -\dfrac{1}{2}< \dfrac{5}{-24}.Vậy:-\dfrac{8}{15}< \dfrac{5}{-24}\\ h,\dfrac{69}{-230}=\dfrac{69:23}{-230:23}=\dfrac{3}{-10};\dfrac{-39}{143}=\dfrac{-39:13}{143:13}=\dfrac{-3}{11}\\ Vì:\dfrac{-3}{10}< -\dfrac{3}{11}.Vậy:\dfrac{69}{-230}< \dfrac{-39}{143}\\ i,\dfrac{7}{41}=1-\dfrac{34}{41};\dfrac{13}{47}=1-\dfrac{34}{47}\\ Vì:\dfrac{34}{41}>\dfrac{34}{47}.Nên:1-\dfrac{34}{41}< 1-\dfrac{34}{47}.Vậy:\dfrac{7}{41}< \dfrac{13}{47}\)










9.
a) \(7^3<7^5\)
b) \(9^{12}<11^{12}\)
c) \(1^{14}=1^{13}\)
d) \(46^7<47^8\)
10.
a) Ta có:
\(13^2=169\)
\(6^3=216\)
Vì 169 < 216 nên \(13^2<6^3\)
b) Ta có:
\(6^2+8^2=36+64=100\)
\(\left(6+8\right)^2=14^2=196\)
Vì 100 < 196 nên \(6^2+8^2<\left(6+8\right)^2\)
c) Ta có:
\(13^2-9^2=169-81=88\)
\(\left(13-9\right)^2=4^2=16\)
Vì 88 > 16 nên \(13^2-9^2>\left(13-9\right)^2\)
d) Ta có:
\(6^3-4^3=216-64=152\)
\(\left(6-4\right)^3=2^3=8\)
Vì 152 > 8 nên \(6^3-4^3>\left(6-4\right)^3\)
Bài 7:
a: \(2+3^2+4^2+13^2\)
\(=2+9+16+169\)
\(=11+185=196=14^2\)
b: \(1^3+2^3+3^3+4^3+5^3+6^3\)
=1+8+27+64+125+216
=441=\(21^2\)
c: \(5^3+6^2+8^2\)
=125+36+64
=125+100
=225
=\(15^2\)
d: \(1^3+2^3+3^3+4^3+5^3\)
=1+8+27+64+125
=225
\(=15^2\)
Bài 8:
\(Q=2^3+4^3+\cdots+20^3\)
\(=2^3\left(1^3+2^3+\cdots+10^3\right)\)
\(=2^3\cdot3025=3025\cdot8=24200\)
Bài 6:
a: \(A=2^2\cdot5^2-3^2-10\)
=100-9-10
=81
\(=9^2\)
b: \(B=3\left(5^2-4^2\right)\)
\(=3\cdot\left(25-16\right)=3\cdot9=27=3^3\)
c: \(C=5\cdot4^3+2^4\cdot5\)
\(=5\cdot\left(64+16\right)\)
\(=5\cdot80=400=20^2\)
d: \(D=5^3+6^3+7^3+79\cdot2^2\)
=125+216+343+316
=1000
\(=10^3\)
5. a) A= \(\left(2^9\cdot3+2^9\cdot5\right):2^{12}\)
=\(2^9\left(3+5\right):2^{12}\)
= \(2^9\cdot2^3:2^{12}\)
= \(1\)
b). <=> \(B=\left\lbrack2^9\left(16+34\right)\right\rbrack:2^{10}\)
= \(\left(2^9\cdot50\right):2^{10}\)
= \(\left(2^9\cdot50\right):\left(2^9\cdot2\right)\)
= 25
c)\(\left(3^4\cdot57-9^2\cdot21\right):3^5\)
= \(\left\lbrack3^4\left(57-21\right)\right\rbrack:3^5\)
= \(\left(3^4\cdot36\right):\left(3^4\cdot3\right)\)
= 12
d) \(D=\left(3^8\cdot17+3^9\cdot5\right):3^7\cdot2^5\)
= \(3^8\left(17+15\right):\left(3^7\cdot32\right)\)
= \(\left(3^8\cdot32\right):\left(3^7\cdot32\right)\)
= 3
e) nhận thấy \(\left(65\cdot111-13\cdot15\cdot37\right)\)
= \(\left(65\cdot111-13\cdot5\cdot3\cdot37\right)\)
= \(\left(65\cdot111-65\cdot111\right)=0\)
bài 6:
a) \(A=2^2\cdot5^2-3^2-10\)
= \(4\cdot25-9-10\)
= \(81=9^2\)
b) \(B=3\cdot\left(5^2-4^2\right)\)
\(B=3\cdot9=27=3^3\)
c) \(C=5\cdot4^3+2^4\cdot5\)
= \(5\left(4^3+2^4\right)\)
= \(5\cdot80\)
= \(400=20^2\)
d) \(D=5^3+6^3+7^3+79\cdot2^2\)
= \(125+216+343+79\cdot4\)
= \(1000=10^3\)
bài 7:
a) \(2+3^2+4^3+13^2\)
= \(2+9+16+169\)
= \(196=14^2\)
b) \(1^3+2^3+3^3+4^3+5^3+6^3\)
= \(1+8+27+64+125+216\)
= \(441=21^2\)
c) \(5^3+6^2+8^2\)
= \(125+36+64\)
= \(225=15^2\)
d) \(1^3+2^3+3^3+4^3+5^3\)
ta có công thức \(1^3+\cdots+n^3=\left(1+\cdots+n\right)^2\)
= \(\left(1+2+3+4+5\right)^2=15^2\)
bài 8:
<=> Q=\(8\left(1^3+2^3+..+10^3\right)\)
=> Q= \(8\cdot3025=24200\)
bài 9:
a) \(7^3<7^5\)
b) \(9^{12}<11^{12}\)
c) \(1^{14}=1^{13}\)
d) \(46^7<47^8\)
bài 10:
a) ta có \(13^2=169<6^3=216\)
b) ta có: \(6^2+8^2=100<\left(6+8\right)^2=196\)
c) ta có: \(13^2-9^2=88>\left(13-9\right)^2=16\)
d) ta có: \(6^3-4^3=152>\left(6-4\right)^3=8\)