Tìm x :
a) x : 6 = 44 + 27 b) x : 4 = 189 - 89
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a) \(\frac{637\times527-189}{526\times637+448}\)
\(=\frac{637\times\left(526+1\right)-189}{526\times637+448}\)
\(=\frac{637\times526+637-189}{526\times637+448}\)
\(=\frac{637+526+448}{526\times637+448}\)
\(=1\)
b) \(\frac{64\times50+44\times100}{27\times38+146\times19}\)
\(=\frac{50\times\left(64+44\times2\right)}{19\times\left(27\times2+146\right)}\)
\(=\frac{50\times\left(64+88\right)}{19\times\left(54+146\right)}\)
\(=\frac{50\times152}{19\times200}\)
\(=\frac{152}{19\times4}\)
\(=\frac{38}{19}\)
\(=\frac{2}{1}\)
\(=2\)
A, 89 -(73-x)=20
=> 73 - x = 89 - 20
=> 73 - x = 69
=> x = 73 - 69
=> x = 4
B, 7x - 2x = 617:615 + 44:11
=> ( 7 - 2 ) x = 36 + 4
=> 5x = 40
=> x = 8
C, x - [ 42+(-28)]=-8
=> x - 14 = - 8
=> x = - 8 + 14
=> x = 6
D, 62 - (2x-3):3=23
=> ( 2x - 3 ) : 3 = 62 - 23
=> ( 2x - 3 ) : 3 = 39
=> 2x - 3 = 117
=> 2x = 120
=> x = 60
E, 4(x-3)=72 - 110
=> 4 ( x - 3 ) = 49 - 1
=> 4 ( x - 3 ) = 48
=> x - 3 = 12
=> x = 15
Bài 5: Tính bằng cách thuận tiện nhất
a) 189 x 6 + 189 x 5 - 189
=189x(6+5-1)
=189x10
=1890
b) 25 x 86 x 4
=25x4x86
=100x86
=8600
HT
Bài 1:
\(A=7^3+7^4+7^5+...+7^{97}+7^{98}.\)
\(A=\left(7^3+7^4\right)+\left(7^5+7^6\right)+...+\left(7^{97}+7^{98}\right).\)
\(A=7^3\left(1+7\right)+7^5\left(1+7\right)+...+7^{97}\left(1+7\right).\)
\(A=7^3.8+7^5.8+...+7^{97}.8.\)
\(A=\left(7^3+7^5+...+7^{97}\right).8⋮8\left(đpcm\right).\)
Vậy.....
Bài 2: Tìm x:
\(3^{47}:\left(189-3x\right)=3^{44}.\)
\(189-3x=3^{47}:3^{44}.\)
\(189-3x=27.\)
\(3x=189-27.\)
\(3x=162.\)
\(x=162:3.\)
\(x=54.\)
Vậy.....
\(27-3.\left(5x+2\right)=6.\)
\(3.\left(5x+2\right)=27-6.\)
\(3.\left(5x+2\right)=21.\)
\(5x+2=21:3.\)
\(5x+2=7.\)
\(5x=7-2.\)
\(5x=5.\)
\(x=5:5.\)
\(x=1.\)
Vậy.....
\(A=7^3+7^4+...+7^{98}\\ \Rightarrow A=\left(7^3+7^4\right)+\left(7^5+7^6\right)+....+\left(7^{97}+7^{98}\right)\\ =7^3\left(1+7\right)+7^5\left(1+7\right)+...+7^{97}\left(1+7\right)\\ =7^3.8+7^5.8+...+7^{97}.8\\ =8\left(7^3+7^5+...+7^{97}\right)⋮8\)
\(a,x:6=44+27\\ x:6=71\\ x=71\times6\\ x=426\)
a) x : 6 = 44 + 27
=> x : 6 = 71
=> x = 71 x 6
=> x = 426
b) x : 4 = 189 - 89
=> x : 4 = 100
=> x = 100 x 4
=> x = 400