tính
b) (7/27+8/27)+12/27 27+(8/27+12/27) c) (4/9+8/9)+3/9 4/9+(8/9+3/9)
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a: 3/4=18/24
9/24=9/24
b: 7/8=35/40
12/40=12/40
c: 9/27=9/27
3/9=9/27
a) 1/2 + 3/4 - (3/4 - 4 - 5)
= 1/2 + 3/4 - 3/4 + 4 + 5
= (3/4 - 3/4) + (4 + 5) + 1/2
= 0 + 9 + 1/2
= 19/2
b) [9/16 + 8/(-27)] - (19/27- 7/16 - 2)
= 9/16 - 8/27 - 19/27 + 7/16 + 2
= (9/16 + 7/16) + (-8/27 - 19/27) + 2
= 1 - 1 + 2
= 2
c) -5/8 . [4/9 + 7/(-12)]
= -5/8 . (-5/36)
= 25/288
d) 7/10 . (-3/5) + 7/10 . (-2/5) - (-3/10)
= 7/10 . (-3/5 - 2/5) + 3/10
= 7/10 . (-1) + 3/10
= -2/5
e) -3/7 . 5/9 + 4/9 . (-3/7) + 2 3/7
= -3/7 . (5/9 + 4/9) + 17/7
= -3/7 . 1 + 17/7
= 2
f) 8 2/7 - (3 4/9 + 4 2/7)
= 8 + 2/7 - 3 - 4/9 - 4 - 2/7
= (8 - 3 - 4) + (2/7 - 2/7) - 4/9
= 1 - 4/9
= 5/9
h) 3.(-1/2)² - (4/5 + 8/15) : 5/6
= 3.1/4 - 4/3 : 5/6
= 3/4 - 8/5
= -17/20
a) 2^7 . 9^3 / 6^5 . 8^2
= 2^7 . 3^9 / 2^5 . 3^5 . 2^6
= 2^-4 . 3^4
Tham khảo :
(Tại mik lười ko mún ghi nên bạn tham khảo cái ảnh này nhá)
\(b=\text{}\dfrac{15.2^{24}.3^{14}-4.3^{15}.2^{24}}{19.2^{24}.3^{14}-6.2^{24}.3^{15}}=\)
\(=\dfrac{2^{24}.3^{14}\left(15-4.3\right)}{2^{24}.3^{14}\left(19-6.3\right)}=3\)
B={x\(\in\)N|x=3k; 1<=k<=4}
C={x\(\in\)N|x=4*a2; 1<=a<=5}
D={x\(\in\)N|x=9*a2;1<=a<=4}
E={x\(\in\)N|x=4k; 0<=x<=4}
G={x\(\in\)N|x=(-3)^k; 1<=k<=4}
b) \(\left(\frac{7}{27}+\frac{8}{27}\right)+\frac{12}{27}\)
\(=\frac{7}{27}+\frac{8}{27}+\frac{12}{27}\)
\(=\frac{27}{27}=1\)
\(27+\left(\frac{8}{27}+\frac{12}{27}\right)\)
\(=27+\frac{20}{27}\)
\(=\frac{729}{27}\)
c) \(\left(\frac{4}{9}+\frac{8}{9}\right)+\frac{3}{9}\)
\(=\frac{4}{9}+\frac{8}{9}+\frac{3}{9}\)
\(=\frac{15}{9}=\frac{5}{3}\)
\(\frac{4}{9}+\left(\frac{8}{9}+\frac{3}{9}\right)\)
\(=\frac{15}{9}=\frac{5}{3}\)
#H
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