\(=\dfrac{4}{9}\cdot\dfrac{9}{5}+\dfrac{1}{4}\cdot\dfrac{1}{10}=\dfrac{4}{5}+\dfrac{1}{40}=\dfrac{33}{40}\)
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Bài 2: Cộng, trừ số hữu tỉ
Các câu hỏi tương tự
Tính bằng cách hợp lí :
S= 3/4 - 0,25 - [ 7/3 + ( -9/2 )] - 5/6
5 mũ 2 nhân 25 mũ 4 trên 125 mũ 3
B= 0,25 +3/5 - (1/8-2/5+\(1\dfrac{1}{4}\) )
C=\(\dfrac{2}{3}-\left(\dfrac{-1}{4}\right)+\dfrac{3}{5}-\dfrac{7}{45}-\left(\dfrac{-5}{9}\right)+\dfrac{1}{12}+\dfrac{1}{35}\)
D=\(\left(5-\dfrac{3}{4}+\dfrac{1}{5}\right)-\left(6+\dfrac{7}{4}-\dfrac{8}{5}\right)-\left(2-\dfrac{5}{7}+\dfrac{16}{5}\right)\)
chứng minh rằng 1/2 mũ 2 + 1/3 mũ 2+ 1/4 mũ 2+.....+ 1/1990 mũ 2 < 3/4
Tìm x, biết
a. x + \(\dfrac{3}{10}=\dfrac{-2}{15}\)
b. \(\dfrac{-11}{12}x+0,25=\dfrac{5}{6}\)
c. x + (x+1)+(x+2)+........................+(x+2002)=2004
Bài 6 : Tính giá trị các biểu thức .
a. A = -5/7 + 7/-5 + 4/7 + 7/4 .
b. B = 2/-5 + -3/7 + -7/10 + 3/-8 .
c. C = -5/7 + 2/-7 + 4/-9 + 4/9 .
d. D = ( 3 - 3/4 + 2/3 ) - ( 2 + 4/3 - 3/2 ) - ( 1 - 7/3 - 9/2 ) .
-4/5.x-(0,25-x)=-13/3
B = 1/5 - 3/7 + 5/9 -2/11+ 7/13 - 9/16 - 7/13 + 2/11 - 5/9 + 3/7 - 1/5
Tinh:
dfrac{7}{8}.left(dfrac{2}{12}+dfrac{4}{10}right)
dfrac{3}{2}-dfrac{5}{6}:left(dfrac{1}{2}right)^2+sqrt{4}
dfrac{15}{34}+dfrac{7}{21}+dfrac{19}{34}-1dfrac{15}{17}+dfrac{2}{3}
left(-2right)^3.left(dfrac{3}{4}-0,25right):left(2dfrac{1}{4}-1dfrac{1}{6}right)
16dfrac{2}{7}:left(-dfrac{3}{5}right)+28dfrac{2}{7}:left(-dfrac{3}{5}right)
Đọc tiếp
Tinh:
\(\dfrac{7}{8}.\left(\dfrac{2}{12}+\dfrac{4}{10}\right)\)
\(\dfrac{3}{2}-\dfrac{5}{6}:\left(\dfrac{1}{2}\right)^2+\sqrt{4}\)
\(\dfrac{15}{34}+\dfrac{7}{21}+\dfrac{19}{34}-1\dfrac{15}{17}+\dfrac{2}{3}\)
\(\left(-2\right)^3.\left(\dfrac{3}{4}-0,25\right):\left(2\dfrac{1}{4}-1\dfrac{1}{6}\right)\)
\(16\dfrac{2}{7}:\left(-\dfrac{3}{5}\right)+28\dfrac{2}{7}:\left(-\dfrac{3}{5}\right)\)
Tính nhanh
1/5-3/7+5/9-2/11+7/13-9/16-7/13+2/11-5/9+3/7-1/5