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\(b,2^3x5^3-3x\left\{400-\left[673-2^3x\left(7^8:7^6+7^0\right)\right]\right\}\)
\(=1000-3x\left\{400-\left[673-8x\left(7^2+1\right)\right]\right\}\)
\(=1000-3x\left\{400-\left[673-8x50\right]\right\}\)
\(=1000-3x\left\{400-\left[673-400\right]\right\}\)
\(=1000-3x\left\{400-273\right\}\)
\(=1000-3x127\)
\(=1000-381\)
\(=619\)
\(a,1968:16+5136:16-704:16\)
\(=\left(1968+5136-704\right):16\)
\(=6400:16\)
\(=400\)
1968:16+5136:16-704:16
= (1968+5136-704):16
= 6400 :16= 400
a, (-20) + 16 + (-34) + 20 = [(-20) + 20] + [16 + (-34)] = 0 + (-18) = (-18) b, 12 + 3.[39 - (5 - 2)2] = 12 + 3.[39 - 32] = 12 + 3.[39 - 9] = 12 + 3.30 = 12 + 90 = 102
Câu 9
a) 2/15 + (-3/5)
= 2/15 - 3/5
= 2/15 - 9/15
= -7/15
b) -5/7 + 3/7 . (-2/9)
= -5/7 - 2/21
= -15/21 - 2/21
= -17/21
c) 5/16 - (7/15 - 3/16) + 17/30
= 5/16 - 7/15 + 3/16 + 17/30
= (5/16 + 3/16) + (17/30 - 14/30)
= 1/2 + 1/10
= 5/10 + 1/10
= 6/10
= 3/5
\(a,\dfrac{2}{15}+\left(-\dfrac{3}{5}\right)\\ =\dfrac{2}{15}-\dfrac{3}{5}\\ =\dfrac{2}{15}-\dfrac{9}{15}\\ =-\dfrac{7}{15}\\ b,-\dfrac{5}{7}+\dfrac{3}{7}\times\left(-\dfrac{2}{9}\right)\\ =-\dfrac{5}{7}-\dfrac{2}{21}\\ =-\dfrac{15}{21}-\dfrac{2}{21}\\ =-\dfrac{17}{21}\\ c,\dfrac{5}{16}-\left(\dfrac{7}{15}-\dfrac{3}{16}\right)+\dfrac{17}{30}\\ =\dfrac{5}{16}-\dfrac{7}{15}+\dfrac{3}{16}+\dfrac{17}{30}\\ =\left(\dfrac{5}{16}+\dfrac{3}{16}\right)-\left(\dfrac{17}{15}+\dfrac{17}{30}\right)\\ =\dfrac{1}{2}-\dfrac{17}{10}\\ =\dfrac{5}{10}-\dfrac{17}{10}\\ =-\dfrac{6}{5}.\)
a) (-124) + 24 = -100
b) 37. 78 + 37. 22
= 37 . ( 78 + 22 )
= 37 . 100
= 3700
\(=\dfrac{2}{3}+\dfrac{1}{5}-\dfrac{2}{3}-4\)
\(=\dfrac{1}{5}-4=\dfrac{-19}{5}\)
6/7+(5/8-3/16):5.-4
=6/7+(10/16-3/16):5.-4
=6/7+7/16:5.-4
=6/7+7/80.-4
=6/7+-28/80
=6/7+7/20
120/140+49/140
=169/140
e: =5/7(5/11+2/11-14/11)
=5/7(-7/11)=-5/11
f: =-5/4(2/11+9/11)+1+3/4
=-5/4+7/4
=2/4=1/2
g: =-5/7(3/13+10/13)+1+5/7
=-5/7+1+5/7
=1
h: =7/4(29/5-9/5)+41/13
=-7+41/13=-50/13
\(1968:16+5136:16-704:16\)
= \(\left(1968+5136-704\right):16\)
= \(6400:16\)
= \(400\).
1968:16+5136:16-704:16
=(1968+5136-704):16
=..................................bạn tự tính