tìm x biết :
a) 12+x=34
b) 23+x=34
c)45+34=x
d)/5x+3/-x=7
a) 12+x=34
x=34-12
x=22
b) 23+x=34
x=34-23
x=11
c)45+34=79
a, 12 + x = 34
x = 34 - 12
x = 22
b, 23 + x = 34
x = 34 - 23
x = 11
c, 45 + 34 = x
x = 79
a) 12+x=34
x=34-12
x=22
b) 23+x=34
x=34-23
x=11
c) 45+23=x
68=x
x=68
Tìm số nguyên x, biết :
a) (2x - 18) : (-10) -34=2
b) 120 : (5x + 20) -45 =75
a) \(\left(2x-18\right):\left(-10\right)-34=2\)
\(\Rightarrow\left(2x-18\right):\left(-10\right)=2+34\)
\(\Rightarrow\left(2x-18\right):\left(-10\right)=36\)
\(\Rightarrow2x-18=36\cdot\left(-10\right)\)
\(\Rightarrow2x-18=-360\)
\(\Rightarrow2x=-360+18\)
\(\Rightarrow2x=-342\)
\(\Rightarrow x=-342:2\)
\(\Rightarrow x=-171\)
b) \(120:\left(5x+20\right)-45=75\)
\(\Rightarrow120:\left(5x+20\right)=75+45\)
\(\Rightarrow120:\left(5x+20\right)=120\)
\(\Rightarrow5x+20=120:120\)
\(\Rightarrow5x+20=1\)
\(\Rightarrow5x=1-20\)
\(\Rightarrow5x=-19\)
\(\Rightarrow x=-\dfrac{19}{5}\)
B1: Tìm x biết:
a, 3x = 81 b, 5 . 4x = 80
c, 2x = 45 : 43 d, 3 . 2x+1 - 32 = 15
e, 5x-1 + 311 : 39 = 34 h, 43 . 4x-1 = 64
a: 3x=81
nên x=27
b: \(5\cdot4^x=80\)
\(\Leftrightarrow4^x=16\)
hay x=2
c: \(2^x=4^5:4^3\)
\(\Leftrightarrow2^x=2^4\)
hay x=4
a) 70-5 (2x-3)=45
b) 6(5x+35)=330
c)936-(4x+24)=72
d)5(3x+34)=515
a) 70 - 5 ( 2x-3 ) = 45
5( 2x-3 ) = 25
2x - 3 = 25 : 5
2x - 3 = 5
2x = 8
x = 8 : 2
x = 4
b) 6 ( 5x + 35 ) = 330
5x + 35 = 330 : 6
5x + 35 = 55
5x = 55 - 35
5x = 20
x = 20 : 5
x = 4
c) 936 - ( 4x + 24 ) = 72
4x + 24 = 936 - 72
4x + 24 = 864
4x = 864 - 24
4x = 840
x = 840 : 4
x = 210
d) 5( 3x + 34 ) = 515
3x + 34 = 515 : 5
3x + 34 = 103
3x = 103 - 34
3x = 69
x = 69 : 3
x = 23
\(a,70-5\left(2x-3\right)=45\)
\(\Leftrightarrow10x-15=70-45\)
\(\Leftrightarrow10x=25+15\)
\(\Leftrightarrow x=\frac{40}{10}=4\)
Vậy x=4
\(b,6\left(5x+35\right)=330\)
\(\Leftrightarrow5x+35=55\)
\(\Leftrightarrow5x=20\)
\(\Leftrightarrow x=4\)
vậy x=4
\(c,936-\left(4x+24\right)=72\)
\(\Leftrightarrow4x+24=936-72\)
\(\Leftrightarrow4x=864-24\)
\(\Leftrightarrow x=840:4=210\)
Vậy x=210
\(d,5\left(3x+34\right)=515\)
\(\Leftrightarrow3x+34=515:5\)
\(\Leftrightarrow3x=103-34\)
\(\Leftrightarrow x=69:3=23\)
Vậy x=23
Bài 1:Rút gọn
a)219×273+15×49×9469×210+1210
b)(−12 )3−(34 )3×(−2)22×(−1)5+(34 )2−38
c)45×94−2×64219×38+68×20
Bài 2:Tìm x
a)5x+5x+2=650
b)
Viết tiếp vào chổ trống:
N h ậ n x é t : 2 3 × 4 5 = . . . , 4 3 × 2 3 = . . . . V ậ y 2 3 × 4 5 . . . . . . 4 5 × 2 3 N h ậ n x é t : ( 1 3 × 2 5 ) × 3 4 = . . . . 1 3 × ( 2 5 × 3 4 ) = . . . . ( 1 3 × 2 5 ) × 3 4 . . . . 1 3 × ( 2 5 × 3 4 ) N h ậ n x é t : ( 1 5 × 2 5 ) × 3 4 = . . . . 1 5 × 3 4 + 2 5 × 3 4 = . . . . V ậ y 1 5 + 2 5 × 3 4 . . . 1 5 × 3 4 + 2 5 × 3 4
Điền dấu >; <, = vào chỗ chấm:
45 + 3 … 50 | 54 – 2 … 54 + 2 |
45 + 30 … 35 + 40 | 54 – 20 … 52 – 40 |
45 + 34 … 34 + 45 | 54 – 24 … 45 – 24 |
Lời giải chi tiết:
45 + 3 < 50 | 54 – 2 < 54 + 2 |
45 + 30 = 35 + 40 | 54 – 20 > 52 – 40 |
45 + 34 = 34 + 45 | 54 – 24 > 45 – 24 |
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Tính nhanh: 1 2 + − 1 2 + − 2 3 + 2 3 + 3 4 + − 3 4 + − 4 5 + 4 5 + 5 6 + − 5 6
1 2 + − 1 2 + − 2 3 + 2 3 + 3 4 + − 3 4 + − 4 5 + 4 5 + 5 6 + − 5 6 = 0
1 2 + − 1 2 + − 2 3 + 2 3 + 3 4 + − 3 4 + − 4 5 + 4 5 + 5 6 + − 5 6 = 0
Đây nha
tìm x thuộc z , biêt
a)3x + 45 . 5x - 45 = 0
b) 3x + 45 . 5x - 45 < 0
c) ( x2 + 3 ) . ( 2x - 2016 ) =0
d) 3x + 45 . 5x - 45 >0
e) 3x + 45 . 5x - 45 = -7