Cho A= 5/9 - 7/8 + 2/3 + 4/9 - 1/8 + 1/3
B= 1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42
a) Tính A và B
b) Tìm C biết:(A- 7B) của C bằng 2010
GIÚP MK VS
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A= 5/9 - 7/8 + 2/3 + 4/9 - 1/8 + 1/3
B= 1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42
a) Tính A và B
b) Tìm C biết: ( A - 7B) của C bằng 2010
BẠN NÀO CÓ LỜI GIẢI CHI TIẾT GIÚP MK, MK SẼ TICK.
Cho A= 5/9 - 7/8 + 2/3 + 4/9 -1/8 +1/3
B= 1/2 + 1/6 +1/12 + 1/20 + 1/30 + 1/42
a) Tính A và B.
b) Tìm C bíêt ( A - 7B) cua C bang 2010.
Cac bn thong cam nha , dien thoai mk ko viet dau dc .Bn nao giup mk , mk se tick.
A=5/9 - 7/8 + 2/3 + 4/9 - 1/8 + 1/3
B= 1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42
a) Tính A và B
b) Tìm C bíêt ( A - 7B) cua C bang 2010
Cau A và B mk dã giai roi , cau A ra 1, B ra 6/7 ,cac bn chi can giup mk cau C thoi , cauC mk ko bt cach giai!!!
Bn nao giup mk , mk se tick.
Tính A và B
A= 5/9 - 7/8 + 2/3 + 4/9 - 1/8 + 1/3
B= 1/2 + 1/6 + 1/12 + 1/20 + 1/20 + 1/30 + 1/42
BẠN NÀO GIÚP MK, MK SẼ TICK
Bài 19: Tìm a biết1/ a + b – c 18 với b 10 ; c -92/ 2a – 3b + c 0 với b -2 ; c 43/ 3a – b – 2c 2 với b 6 ; c -14/ 12 – a + b + 5c -1 với b -7 ; c 55/ 1 – 2b + c – 3a -9 với b -3 ; c -7Bài 20: Sắp xếp theo thứ tự tăng dần1/ 7; -12 ; +4 ; 0 ; │-8│; -10; -12/ -12; │+4│; -5 ; -3 ; +3 ; 0 ; │-5│ * giảm dần3/ +9 ; -4 ; │-6│; 0 ; -│-5│; -(-12)4/ -(-3) ; -(+2) ; │-1│; 0 ; +(-5) ; 4 ; │+7│; -8Giúp mình với
Đọc tiếp
Bài 19: Tìm a biết
1/ a + b – c = 18 với b = 10 ; c = -9
2/ 2a – 3b + c = 0 với b = -2 ; c = 4
3/ 3a – b – 2c = 2 với b = 6 ; c = -1
4/ 12 – a + b + 5c = -1 với b = -7 ; c = 5
5/ 1 – 2b + c – 3a = -9 với b = -3 ; c = -7
Bài 20: Sắp xếp theo thứ tự tăng dần
1/ 7; -12 ; +4 ; 0 ; │-8│; -10; -1
2/ -12; │+4│; -5 ; -3 ; +3 ; 0 ; │-5│ * giảm dần
3/ +9 ; -4 ; │-6│; 0 ; -│-5│; -(-12)
4/ -(-3) ; -(+2) ; │-1│; 0 ; +(-5) ; 4 ; │+7│; -8
Giúp mình với
Tính nhanh:
a,1/4+2/5+6/8+9/15+8/1
b,1/2+2/4+3/6+4/8+5/10+6/12+7/14+8/16+9/18+10/20
c,1/10+4/20+9/30+16/40+25/50+36/60+49/70+64/80+81/90
a; \(\dfrac{1}{4}\) + \(\dfrac{2}{5}\) + \(\dfrac{6}{8}\) + \(\dfrac{9}{15}\) + \(\dfrac{8}{1}\)
= (\(\dfrac{1}{4}\) + \(\dfrac{6}{8}\)) + (\(\dfrac{2}{5}\) + \(\dfrac{9}{15}\)) + \(\dfrac{8}{1}\)
= (\(\dfrac{1}{4}\) + \(\dfrac{3}{4}\)) + (\(\dfrac{2}{5}\) + \(\dfrac{3}{5}\)) + 8
= 1 + 1 + 8
= 2 + 8
= 10
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b; \(\dfrac{1}{2}\) + \(\dfrac{2}{4}\) + \(\dfrac{3}{6}\) + \(\dfrac{4}{8}\) + \(\dfrac{5}{10}\) + \(\dfrac{6}{12}\) + \(\dfrac{7}{14}\) + \(\dfrac{8}{16}\) + \(\dfrac{10}{20}\)
= \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) x (\(\dfrac{2}{2}\) + \(\dfrac{3}{3}\) + \(\dfrac{4}{4}\) + \(\dfrac{5}{5}\)+ \(\dfrac{6}{6}+\dfrac{7}{7}+\dfrac{8}{8}\) + \(\dfrac{10}{10}\))
= \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) x (1 + 1 +1 + 1+ 1+ 1+ 1 +1)
= \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) x 1 x 8
= \(\dfrac{1}{2}\) + \(\)\(\dfrac{1}{2}\) x 8
= \(\dfrac{1}{2}\) + 4
= \(\dfrac{9}{2}\)
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c; \(\dfrac{1}{10}\) + \(\dfrac{4}{20}\) + \(\dfrac{9}{30}\)+\(\dfrac{16}{40}+\dfrac{25}{50}+\dfrac{36}{60}+\dfrac{49}{70}+\dfrac{64}{80}+\dfrac{81}{90}\)
= \(\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}\)
= \(\dfrac{1+2+3+4+5+6+7+8+9}{10}\)
= \(\dfrac{\left(1+9\right)+\left(2+8\right)+\left(3+7\right)+\left(4+6\right)+5}{10}\)
= \(\dfrac{10+10+10+10+5}{10}\)
= \(\dfrac{\left(10+10+10+10\right)+5}{10}\)
= \(\dfrac{10\times4+5}{10}\)
= \(\dfrac{45}{10}\)
= \(\dfrac{9}{2}\)
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Tính nhanh:
a,1/4+2/5+6/8+9/15+8/1
b,1/2+2/4+3/6+4/8+5/10+6/12+7/14+8/16+9/18+10/20
c,1/10+4/20+9/30+16/40+25/50+36/60+49/70+64/80+81/90
a; \(\dfrac{1}{4}\) + \(\dfrac{2}{5}\) + \(\dfrac{6}{8}\) + \(\dfrac{9}{15}\) + \(\dfrac{8}{1}\)
= (\(\dfrac{1}{4}\) + \(\dfrac{6}{8}\)) + (\(\dfrac{2}{5}\) + \(\dfrac{9}{15}\)) + 8
= (\(\dfrac{1}{4}\) + \(\dfrac{3}{4}\)) + (\(\dfrac{2}{5}\) + \(\dfrac{3}{5}\)) + 8
= 1 + 1 + 8
= 2 + 8
= 10
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b; \(\dfrac{1}{2}\) + \(\dfrac{2}{4}\) + \(\dfrac{3}{6}\) + \(\dfrac{4}{8}\) + \(\dfrac{5}{10}\) + \(\dfrac{6}{12}\) + \(\dfrac{7}{14}\) + \(\dfrac{8}{16}\) + \(\dfrac{9}{18}\) + \(\dfrac{10}{20}\)
= \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\) + \(\dfrac{1}{2}\)
= \(\dfrac{1}{2}\) x 10
= 5
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c; \(\dfrac{1}{10}\) + \(\dfrac{4}{20}\) + \(\dfrac{9}{30}\)+\(\dfrac{16}{40}+\dfrac{25}{50}+\dfrac{36}{60}+\dfrac{49}{70}+\dfrac{64}{80}+\dfrac{81}{90}\)
= \(\dfrac{1}{10}+\dfrac{2}{10}+\dfrac{3}{10}+\dfrac{4}{10}+\dfrac{5}{10}+\dfrac{6}{10}+\dfrac{7}{10}+\dfrac{8}{10}+\dfrac{9}{10}\)
= \(\dfrac{1+2+3+4+5+6+7+8+9}{10}\)
= \(\dfrac{\left(1+9\right)+\left(2+8\right)+\left(3+7\right)+\left(4+6\right)+5}{10}\)
= \(\dfrac{10+10+10+10+5}{10}\)
= \(\dfrac{\left(10+10+10+10\right)+5}{10}\)
= \(\dfrac{10\times4+5}{10}\)
= \(\dfrac{45}{10}\)
= \(\dfrac{9}{2}\)
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a,2/9-5/7+20/33+8/21+5/18-6/22
b, 1/2+1/3-1/4+1/6+1/8+1/16+1/32+1/64+1/128
c,5-1/2-5/6-11/12-19/20-29/30
các bn giúp mk nha
bài 2: tính nhanh :
a) 3/8 + 7/12 + 10/16 + 10/24 b) 4/6 + 7/13 + 17/9 + 19/13 + 1/9 + 14/6
c) 1/2 + 1/6 + 1/12 + 1/20 + 1/30 + 1/42 + 1/56
a) \(\dfrac{3}{8}+\dfrac{7}{12}+\dfrac{10}{16}+\dfrac{10}{24}\)
\(=\dfrac{3}{8}+\dfrac{7}{12}+\dfrac{5}{8}+\dfrac{5}{12}\)
\(=\left(\dfrac{3}{8}+\dfrac{5}{8}\right)+\left(\dfrac{7}{12}+\dfrac{5}{12}\right)\)
\(=1+1\)
\(=2\)
b) \(\dfrac{4}{6}+\dfrac{7}{13}+\dfrac{17}{9}+\dfrac{19}{13}+\dfrac{1}{9}+\dfrac{14}{6}\)
\(=\dfrac{2}{3}+\dfrac{7}{13}+\dfrac{17}{9}+\dfrac{19}{13}+\dfrac{1}{9}+\dfrac{7}{3}\)
\(=\left(\dfrac{2}{3}+\dfrac{7}{3}\right)+\left(\dfrac{7}{13}+\dfrac{19}{13}\right)+\left(\dfrac{17}{9}+\dfrac{1}{9}\right)\)
\(=3+2+2\)
\(=7\)
c) \(\dfrac{1}{2}+\dfrac{1}{6}+\dfrac{1}{12}+\dfrac{1}{20}+\dfrac{1}{30}+\dfrac{1}{42}+\dfrac{1}{56}\)
\(=\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+\dfrac{1}{4\cdot5}+\dfrac{1}{5\cdot6}+\dfrac{1}{6\cdot7}\)
\(=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{5}+\dfrac{1}{5}-\dfrac{1}{6}+\dfrac{1}{6}-\dfrac{1}{7}\)
\(=1-\dfrac{1}{7}\)
\(=\dfrac{6}{7}\)
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