22 ( x + 23 ) - 5 = 55
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14x + 54 = 82
175 + (30 - x) = 2001
1551- 10 (x + 1) = 55
5 . (x + 12) + 22 = 92
6 . (x + 23) + 40 = 100
14x + 54 = 82
14x = 28
x = 2
175 + (30 - x) = 2001
30 - x = 1826
x = 30 - 1826
x = - 1796
1551 - 10 ( x + 1 ) = 55
10(x + 1) = 1496
x + 1 = 149,6
x = 148,6
5 . (x + 12) + 22 = 92
5 . (x + 12) = 70
x + 12 = 14
x = 2
6 . (x + 23) + 40 = 100
6 . (x + 23) = 60
x + 23 = 10
x = - 13
\(14x+54=82\)
\(\Leftrightarrow14x=82-54\)
\(\Leftrightarrow14x=28\)
\(\Leftrightarrow x=2\)
Vậy \(x=2\)
\(175+\left(30-x\right)=2001\)
\(\Leftrightarrow30-x=2001-175\)
\(\Leftrightarrow30-x=1826\)
\(\Leftrightarrow x=-1796\)
Vậy \(x=-1796\)
\(1551-10\left(x+1\right)=55\)
\(\Leftrightarrow10.\left(x+1\right)=1551-55\)
\(\Leftrightarrow10.\left(x+1\right)=1496\)
\(\Leftrightarrow x+1=\frac{1496}{10}\)
\(\Leftrightarrow x=\frac{1486}{10}\)
Vậy \(x=\frac{1486}{10}\)
\(5.\left(x+12\right)+22=92\)
\(\Leftrightarrow5.\left(x+12\right)=70\)
\(\Leftrightarrow x+12=14\).
\(\Leftrightarrow x=2\)
Vậy \(x=2\)
\(6.\left(x+23\right)+40=100\)
\(\Leftrightarrow6.\left(x+23\right)=60\)
\(\Leftrightarrow x+23=10\)
\(\Leftrightarrow x=-13\)
Vậy \(x=-13\)
Bài 3
\(\dfrac{55}{23}+\dfrac{-22}{23}\le x\le\dfrac{1}{5}-\dfrac{-1}{6}+\dfrac{79}{30}\)
\(=\dfrac{33}{23}\)\(\le x\le\dfrac{90}{30}\)
\(=\dfrac{33}{23}\le x\le3\)
Mà \(x\in Z\) \(\Rightarrow\)\(x=2\)
Có 1 giá trị thỏa mãn
Chọn A
Bài 4
\(\dfrac{-11}{12}< \dfrac{5}{x}< \dfrac{-11}{15}\)
Chọn D
Bài 5
\(M=\dfrac{1}{1\cdot2}+\dfrac{1}{2\cdot3}+\dfrac{1}{3\cdot4}+...+\dfrac{1}{99\cdot100}\)
\(M=1-\dfrac{1}{2}+\dfrac{1}{2}-\dfrac{1}{3}+\dfrac{1}{3}-\dfrac{1}{4}+\dfrac{1}{4}-\dfrac{1}{99}+\dfrac{1}{99}-\dfrac{1}{100}\)
\(M=1-\dfrac{1}{100}\)
\(M=\dfrac{100}{100}-\dfrac{1}{100}\)
\(M=\dfrac{99}{100}\)
CHọn C
a, Ta có :
A = 1 + 2 + 2 2 + 2 3 + 2 4 + . . . + 2 99 + 2 100
2A = 2 + 2 2 + 2 3 + 2 4 + . . . + 2 99 + 2 100 + 2 101
A = 2A – A = ( 2 + 2 2 + 2 3 + 2 4 + . . . + 2 99 + 2 100 + 2 101 ) –( 1 + 2 + 2 2 + 2 3 + 2 4 + . . . + 2 99 + 2 100 )
= 2 + 2 2 + 2 3 + 2 4 + . . . + 2 99 + 2 100 + 2 101 – 1 - 2 - 2 2 - 2 3 - 2 4 - . . . - 2 99 - 2 100
= 2 101 - 1
Vậy A = 2 101 - 1
b, Ta có.
B = 5 + 5 3 + 5 5 + . . . + 5 97 + 5 99
5 2 B = 5 2 ( 5 + 5 3 + 5 5 + . . . + 5 97 + 5 99 )
25B = 5 3 + 5 5 + . . . + 5 97 + 5 99 + 5 101
25B – B = ( 5 3 + 5 5 + . . . + 5 97 + 5 99 + 5 101 ) – ( 5 + 5 3 + 5 5 + . . . + 5 97 + 5 99 )
24B = 5 3 + 5 5 + . . . + 5 97 + 5 99 + 5 101 – 5 - 5 3 - 5 5 - . . . - 5 97 - 5 99
24B = 5 101 - 5
B = 5 101 - 5 24 = 5 5 100 - 1 24
Vậy B = 5 5 100 - 1 24
\(\frac{9}{5}\)S = 9+99+...+99...9 (50 chữ số 9)
=10-1+102-1+...+1050-1
=(10+102+...+1050)-(1+1+...+1)
=(1051-10) - 50
=1051-60
\(\Rightarrow\)S=(1051-60)/\(\frac{9}{5}\)= 5(1051-60)/9
Ta có công thức tính dãy số trên :
\(S=\dfrac{K}{9}\left(\dfrac{10^{n+1}-}{9}-\left(n+1\right)\right)\)
\(=\dfrac{5}{9}\left(\dfrac{10^{51}-1}{9}-51\right)=6,172839506\times10^{49}\)
\(\text{a.61 x 23 + 39 x 22}\)
\(=61.22+1+39.22\)
\(=22.\left(61+39\right)+1\)
\(=22.100+1\)
\(=2200+1\)
\(=2201\)
mình chỉ làm được 1 câu thôi
hok tốt
2^2(x+2^3)-5=55
4(x+8)-5=55
4(x+8) =55+5
4(x+8) =60
x+8 =60/4
x+8 =15
x =15-8
x =7
Vậy x=7
22 . (x + 23) - 5 = 55
4 . (x + 8) = 55 + 5
4 . (x + 8) = 60
x + 8 = 60 : 4
x + 8 = 15
x = 15 - 8
x = 7
Vậy x= 7
Ủng hộ mk nha !!! ^_^