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b,\(7^5\)\(.(3x-2^3\)\()=7^6\)
\(3x-2^3\)\(=7^6:7^5=7^1=7\)
\(3x=7+8\)
\(3x=15\)
\(x=15:3\)
\(x=5\)
c,\(96-3(x-5)=57\)
\(3(x-5)=96-57\)
\(3(x-5)=39\)
\(x-5=39:3\)
\(x-5=13\)
\(x=13+5\)
\(x=18\)
d,\([(6x-72):2-84].28=5628\)
\((6x-72):2-84=5628:28\)
\((6x-72):2-84=201\)
\((6x-72):2=201+84\)
\((6x-72):2=285\)
\((6x-72)=285.2\)
\(6x-72=570\)
\(6x=570+72\)
\(6x=642\)
\(x=642:6\)
\(x=107\)
b)
75 . ( 3x - 23 ) = 74 . 72
75 . ( 3x - 8 ) = 76
3x - 8 = 7
3x = 15
x = 5.
Vậy x = 5.
c)
96 - 3( x - 5 ) = 57
3( x - 5 ) = 39
x - 5 = 13
x = 18.
Vậy x = 18.
d)
[ ( 6x - 72 ) : 2 - 84 ] . 28 = 5628
( 6x - 72 ) : 2 - 84 = 201
( 6x - 72 ) : 2 = 285
6x - 72 = 570
6x = 642
x = 107.
Vậy x = 107.
B1. 2x + 3 + 22 = 72
=> 2x + 3 + 4 = 72
=> 2x + 3 = 72 - 4
=> 2x + 3 = 68
=> ko có gtri x
B2 : Ta có : A = 1 + 2 + 22 + 23 + 24 + 25 + 26 + ... + 22001 + 22002
= (1 + 2) + (22 + 23 + 24) + (25 + 26 + 27) + ... + (22000 + 22001 + 22002)
= 3 + 22.(1 + 2 + 22) + 25.(1 + 2 + 22 ) + ... + 22000 . (1 + 2 + 22)
= 3 + 22.7 + 25.7 + ... + 22000 . 7
= 3 + (22 + 25 + .... + 22000) . 7
=> Số dư của 7 là 3
Bài 1a:
A = 2 + 2^2 + 2^3+ ...+ 2^100
2A = 2^2 + 2^3 + ...+ 2^101
2A - A = 2^2 + 2^3 + ...+ 2^101 - 2 - 2^2 - 2^3 - ... - 2^100
A = (2^2 - 2^2) + (2^3 - 2^3) + ... + (2^100 - 2^100) + (2^101 - 2)
A = 0+ 0+ 0 + ...+ 0 + 2^101 - 2
A = 2^101 - 2
Bài 2a:
A = 7^6 + 7^5 - 7^4
A = 7^4.(7^2 + 7 - 1)
A =7^4.(49 + 7 - 1)
A =7^4.(56 - 1)
A =7^4.55
A = 7^3.(7.11).5
A = 7^3.77.5 ⋮ 77 (đpcm)
a ) số đối : -9 = 9 ; 17 = 17
b ) 63 = 216 ; 70 = 1
Bài 2 :
a) 42
b) 30
c) 3800
Bài 3 :
a) x = -31
b) x = 2
c) x = { -2 ;-1 ; 0 ;1;2;3;4 }
1/a.9;-17.
b.216;1
2/a.42;b.30;c.3800
3/a.x=-31;b.x=2;c.x=-2;-1;0;1;2;3;4.
\(5^x+5^{x+2}=650;5^x.26=650;5^x=25;x=2\)
\(2^x+2^{x+3}=144;2^x.9=144;2^x=16;x=4\)
\(3^{x-1}+5.3^{x-1}=162;3^{x-1}.6=162;3^{x-1}=27;x=4\)
\(\left(x-5\right)^4=\left(x-5\right)^6\)
\(\rightarrow x-5=0\&x-5=1\) hoặc x - 5 = - 1
\(x-5=1;x=6;x-5=0;x=5;x-5=-1;x=4\)
\(\left(2^2:4\right).2^n=4;2^n=2^2;n=2\)
b)75. (3x - 23) = 74 .72
\(3x-8=7^6:7^5\)
\(3x-8=7\)
\(3x=15\)
\(x=5\)
\(\text{c) 96 - 3(x - 5) = 57}\)
\(3.\left(x-5\right)=39\)
\(x-5=13\)
\(x=18\)
\(\text{d) [(6x - 72):2 - 84].28 = 5628}\)
\(\left(6x-72\right):2-84=201\)
\(\left(6x-72\right):2=285\)
\(6x-72=142,5\)
\(6x=214,5\)
\(x=35,75\)
chúc bạn học tốt
x=5
x=18
x=35,75
\(7^5.\left(3x-2^3\right)=7^4.7^2\)
\(\Leftrightarrow3x-8=7^6:7^5\)
\(\Leftrightarrow3x-8=7\)
\(\Leftrightarrow3x=15\)
\(\Leftrightarrow x=5\)
b)75. (3x - 23) = 74 .72
3x - 23 = 74 .72 : 75
3x - 8 = 7
3x = 7 + 8
3x = 15
x = 15 : 3
x = 5
Vậy x = 5
c) 96 - 3(x - 5) = 57
3(x -5) = 96 - 57
3(x - 5)=39
x - 5 = 39:3
x - 5 = 13
x = 13 + 5
x = 18
Vậy x = 18