-Tìm a,b,c,d biết
a+b+c+d=1
a+c+d=2
a+b+d=3
a+b+c=4
-Tính nhanh
1-4+7-10+...+28-31
giải nhanh hộ mình nhé trước thứ 7 càng tốt
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a) A = \(9\frac{3}{8}-\left(2\frac{3}{5}+2\frac{3}{8}\right)=9\frac{3}{8}-2\frac{3}{5}-2\frac{3}{8}=\left(9\frac{3}{8}-2\frac{3}{8}\right)-2\frac{3}{5}=7-\frac{13}{5}=\frac{22}{5}\)
b) B = \(\left(15\frac{3}{5}+5\frac{3}{4}\right)-8\frac{3}{5}=15\frac{3}{5}+5\frac{3}{4}-8\frac{3}{5}=\left(15\frac{3}{5}-8\frac{3}{5}\right)+5\frac{3}{4}=7+\frac{23}{4}=\frac{51}{4}\)
c) C = \(17\frac{1}{4}-\left(2\frac{3}{7}+7\frac{1}{4}\right)=17\frac{1}{4}-2\frac{3}{7}-7\frac{1}{4}=\left(17\frac{1}{4}-7\frac{1}{4}\right)-2\frac{3}{7}=10-\frac{17}{7}=\frac{53}{7}\)
d) D = \(\left(11\frac{5}{17}+3\frac{5}{7}\right)-4\frac{5}{17}=11\frac{5}{17}+3\frac{5}{7}-4\frac{5}{17}=\left(11\frac{5}{17}-4\frac{5}{17}\right)+3\frac{5}{7}=7+\frac{26}{7}=\frac{75}{7}\)
a)29 . (19 – 13) – 19 . (29 – 13)
= 29 . 6 – 19 . 16
= 174 – 304
= –130.
b)31.(-18)+31.(-81)-31
= 31. [-18 + (-81) - 1 ]
= 31. (-100)
= -3100
c)(7.3-3):(-6)
(7.3-3):(-6)
= (21-3):(-6)
= 18 : (-6)
= 3
d)72:[(-6).2+4)]
= 72 : ( -12 + 4 )
= 72 : -8
= -9
Bài 1
a) (3x - 2⁴).7³ = 2.7⁴
3x - 16 = 2.7⁴ : 7³
3x - 16 = 2.7
3x - 16 = 14
3x = 14 + 16
3x =30
x = 30 : 3
x = 10
b) x - [42 + (-28)] = -8
x - 14 = -8
x = -8 + 14
x = 6
c) 4 - 7.x = x - (13 - 4)
x + 7x = 4 + 9
8x = 13
x = 13/8
Bài 1: a, (3\(x\) - 24 ).73 = 2.74
3\(x\) - 24 = 2.74 : 73
3\(x\) - 16 = 14
3\(x\) = 30
\(x\) = 10
b, \(x\) - (42 + (-28) ] = -8
\(x\) - 14 = -8
\(x\) = 14 - 8
\(x\) = 6
c, 4 - (7\(x\)) = \(x\) - (13 - 4)
4 - 7\(x\) = \(x\) - 9
\(x\) + 7\(x\) = 4 + 9
8\(x\) = 13
\(x\) = \(\dfrac{13}{8}\)
Ta có : a : b : c : d = 2 : 3 : 4 :5
=> a/2 = b/3 = c/4 = d/5 = 3a/6 = b/3 = 2c/8 = 4d/20
= \(\frac{3a+b-2c+4d}{6+3-8+20}\)= \(\frac{105}{21}\)= 5
\(\frac{a}{2}\)= 5 => a = 10
\(\frac{b}{3}\)= 5 => b = 15
\(\frac{c}{4}\)= 5 => c = 20
\(\frac{d}{5}\)= 5 => d = 25
\(a,x:\left(-\frac{15}{28}\right)=\frac{21}{35}\)
\(x=\frac{21}{35}\times\left(-\frac{15}{28}\right)\)
\(x=-\frac{9}{28}\)
\(b,x-\frac{1}{42}=-\frac{6}{7}\times\frac{5}{7}\)
\(x-\frac{1}{42}=-\frac{30}{49}\)
\(x=-\frac{30}{49}+\frac{1}{42}\)
\(x=-\frac{173}{294}\)
\(c,\left(x-\frac{3}{4}\right):\frac{7}{5}=-\frac{1}{4}\)
\(x-\frac{3}{4}=-\frac{1}{4}\times\frac{7}{5}\)
\(x-\frac{3}{4}=-\frac{7}{20}\)
\(x=-\frac{7}{20}+\frac{3}{4}\)
\(x=\frac{2}{5}\)
a)x:-15/28=21/35
x=21/35.-15/28
x=-9/28
b)x-1/42= -6/7.5/7
x-1/42= -6/7.5/7
x-1/42=-30/49
x=-30/49+1/42
x=-173/294
c)(x-3/4):7/5=-1/4
x-3/4=-1/4.7/5
x-3/4=-7/20
x=-7/20+3/4
x=2/5
có gì sai xin tha thứ giùm nha!
hi hi!!!