Cho M = 21 31 + − 16 7 + 44 53 + 10 31 + 9 53 và N = 1 2 + − 1 5 + − 5 7 + 1 6 + − 3 35 + 1 3 + 1 41 . Chọn câu đúng.
A. M = 2 7 ; N = 1 41
B. M = 0 ; N = 1 41
C. M = − 16 7 ; N = 83 41
D. M = − 2 7 ; N = 1 41
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\(\left(\dfrac{21}{31}+\dfrac{-16}{7}\right)+\left(\dfrac{44}{53}+\dfrac{10}{31}\right)+\dfrac{9}{53}.\)
\(\dfrac{21}{31}-\dfrac{16}{7}+\dfrac{44}{53}+\dfrac{10}{31}+\dfrac{9}{53}=\left(\dfrac{21}{31}+\dfrac{10}{31}\right)+\left(\dfrac{44}{53}+\dfrac{9}{53}\right)-\dfrac{16}{7}=1+1-\dfrac{16}{7}=\dfrac{-2}{7}.\)
\(\left(\frac{3}{4}+\frac{2}{11}-\frac{8}{13}\right)+\left(\frac{1}{4}-\frac{5}{13}\right)\)
\(=\frac{3}{4}+\frac{2}{11}-\frac{8}{13}+\frac{1}{4}-\frac{5}{13}\)
\(=\left(\frac{3}{4}+\frac{1}{4}\right)+\frac{2}{11}-\left(\frac{8}{13}+\frac{5}{13}\right)\)
\(=1+\frac{2}{11}-1\)
\(=\frac{2}{11}\)
\(\left(\frac{9}{53}+\frac{21}{31}\right)+\left(\frac{44}{53}-\frac{16}{7}\right)+\frac{10}{31}\)
\(=\frac{9}{53}+\frac{21}{31}+\frac{44}{53}-\frac{16}{7}+\frac{10}{31}\)
\(=\left(\frac{9}{53}+\frac{44}{53}\right)+\left(\frac{21}{31}+\frac{10}{31}\right)-\frac{16}{7}\)
\(=1+1-\frac{16}{7}\)
\(=2-\frac{16}{7}\)
\(=\frac{14}{7}-\frac{16}{7}\)
\(=\frac{-2}{7}\)
Tính
\(\left(\frac{21}{31}+\frac{2013}{6039}\right)-\left(\frac{44}{53}-\frac{10}{31}\right)-\frac{9}{53}\)
\(=\frac{21}{31}+\frac{1}{3}-\frac{44}{53}+\frac{10}{31}-\frac{9}{53}\)
\(=\left(\frac{21}{31}+\frac{10}{31}\right)+\left(-\frac{44}{53}-\frac{9}{53}\right)+\frac{1}{3}\)
\(=1+\left(-1\right)+\frac{1}{3}=0+\frac{1}{3}=\frac{1}{3}.\)
a, -3/4 + 3/7 + -1/4 + 4/9 + 4/7
=\(\left(\frac{-3}{4}+\frac{-1}{4}\right)+\left(\frac{3}{7}+\frac{4}{7}\right)+\frac{4}{9}\)
=\(-1+1+\frac{4}{9}\)
=\(\frac{4}{9}\)
b, -7/9 x 4/11 + -7/9 x 7/11 + 5 và 7/9
\(=\frac{7}{9}x\frac{-4}{11}+\frac{7}{9}x\frac{-7}{11}+5x\frac{7}{9}\)
\(=\frac{7}{9}x\left(\frac{-4}{11}+\frac{-7}{11}+5\right)\)
\(=\frac{7}{9}x4\)
\(=\frac{28}{9}\)
c, ( 21/31 + 2013/6039 ) - ( 44/53 - 10/31) - /53
\(\left(\frac{21}{31}+\frac{2013}{6039}\right)-\left(\frac{44}{53}-\frac{10}{31}\right)-\frac{9}{53}\)
\(=\frac{21}{31}+\frac{1}{3}-\frac{44}{53}+\frac{10}{31}-\frac{9}{53}\)
\(=\left(\frac{21}{31}+\frac{10}{31}\right)+\left(\frac{-44}{53}-\frac{9}{53}\right)+\frac{1}{3}\)
\(=1+\left(-1\right)+\frac{1}{3}\)
\(=\frac{1}{3}\)
Bài 1: Ta chỉ cần bỏ ngoặc rồi cộng hai phân số để ra kết quả là số tự nhiên là xong
Bài 2:
A = \(\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+............+\frac{1}{2003.2004}\)
A = \(1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-.............-\frac{1}{2003}+\frac{1}{2003}-\frac{1}{2004}\)
A = \(1-\frac{1}{2004}\)
A = \(\frac{2004}{2004}-\frac{1}{2004}=\frac{2003}{2004}\)
Mk làm mẫu 1 bài nha
Bài 1 :
a, = (1/4+3/4) - (5/13+8/13)+2/11
= 1 - 1 + 2/11
= 2/11
Tk mk nha
bỏ ngoặc: 21/31+2013/6039-44/53+10/31-9/53
ta có ; (21/31+10/31)-(44/53+9/53)+1/3
1-1+1/3=1/3
(21/31+2013/6039)-(44/53-10/31)-9/53
=21/31+1/3-44/53+10/31-9/53
=(21/31+10/31)-(44/53+9/53)+1/3
=31/31-53/53+1/3
=1-1+1/3
=0+1/3
=1/3!!!
Đáp án cần chọn là: D
M = 21 31 + − 16 7 + 44 53 + 10 31 + 9 53 M = 21 31 + − 16 7 + 44 53 + 10 31 + 9 53 M = 21 31 + 10 31 + 44 53 + 9 53 + − 16 7 M = 1 + 1 + − 16 7 M = 2 + − 16 7 M = − 2 7
N = 1 2 + − 1 5 + − 5 7 + 1 6 + − 3 35 + 1 3 + 1 41 N = 1 2 + 1 6 + 1 3 + − 1 5 + − 5 7 + − 3 35 + 1 41 N = 3 + 1 + 2 6 + − 7 + − 25 + − 3 35 + 1 41 N = 1 + − 1 + 1 41 N = 1 41