{23 + [1 + (3 - 1)2 ]} :13
14 + 2. 82
2.32 - 24: (6.2)
1.So sánh:
a, 2 mũ 6 và 6 mũ 2
b, 73+1 và 7 và 73 + 1
c, 1314 - 1313 và 1315 - 1314
d, 32+n và 23+n (n e N *)
2. Rút gọn mỗi biểu thức sau:
a) A= 1+3+32+33+.....+399+3100
b) B= 2100-299+298-297+....-23+22-2+1
Tính giá trị của biểu thức:
a) \(36 – 18:6\)
b) \(2.3^{2} – 24:6.2\).
c) \(2.3^{2} – 24:(6.2)\).
a) \(36 – 18:6 = 36 – 3 = 33\)
b) \(2.3^{2} + 24 : 6 . 2 = 2.9 + 4.2 = 18 + 8 = 26\)
c) \(2.3^{2} – 24 : (6.2) = 2.9 - 24 : 12 = 18 - 2 = 16.\)
a, 36-18:6=33 b, 2.3\(^2\)+24:6.2=26 c,2.32-24:(.2)=16
giúp mik nha
4.10-x:2=1
5.x:4+3*2=7
6.2:x+5=6
7.2*x*3*5=30
8.2*x:10*2=1
9.18:x-5*2=8
10.5*5-2:x=24
a) 10 - x : 2 = 1
x: 2 = 9
x = 18
b) x:4 + 3 x 2 = 7
x:4 + 6 = 7
x:4 = 1
x = 4
c) 2: x + 5 = 6
2: x = 1
x = 2
+4.10-x:2=1
40-x:2=1
x:2=40-1
x:2=39
x:2=19,5
+5.x:4+3*2=7
5.x:4+6=7
5.x:4=7-6=1
5.x=1.4=4
x=4:5
x=0,8
+6.2:x+5=6
12:x=6-5
12:x=1
x=12:1
x=12
+7.2*x*3*5=30
14.x.15=30
14.x=2
x=2:14
x=1/7
+8.2*x:10*2=1
16.x:20=1
16.x=20
x=20:16
x=1,25
9.18:x-5*2=8
10.5*5-2:x=24
d) 2 * x * 3 * 5 = 30
x * 30 = 30
x = 1
e) 2 * x : 10* 2 = 1
2*x * 1/10 * 2 = 1
2/5 * x = 1
x = 5/2
g) 18 : x - 5*2 = 8
18 : x - 10 = 8
18 : x = 18
x = 1
h) 5*5 -2 : x = 24
25 - 2:x = 24
2:x = 1
x = 2
(23×23×24+24)+(1+2+3+4+....+2019+2020)
Tính nhanh 1/(1+2)+ 1/(2+3)+......1/(23+24)+ 1/(24+25)
giúp mik nha
tìm x:
4.10-x:2=1
5.x:4+3*2=7
6.2:x+5=6
7.2*x*3*5=30
8.2*x:10*2=1
9.18:x-5*2=8
10.5*5-2:x=24
nhớ làm thẳng cột nha.hihi
\(4) 10-x:2=1 \)
\(=> x:2=10-1\)
\(=> x:2=9\)
\(=> x=9.2\)
\(=> x=18\). Vậy \(x=18\)
\(5) x:4+3.2=7\)
\(=> x:4+6=7\)
\(=> x:4=7-6\)
\(=> x:4=1\)
\(=> x=4\). Vậy \(x=4\)
\(6) 2:x+5=6\)
\(=> 2:x=6-5\)
\(=> 2:x=1\)
\(=> x=2\).Vậy \(x=2\)
\(7) 2.x.3.5=30\)
\(=> 2x.15=30\)
\(=>2x=30:15\)
\(=> 2x=2\)
\(=> x=1\).Vậy \(x=1\)
\(8)2.x:10.2=1\)
\(=> 2x=1:2.10\)
\(=> 2x=5\)
\(=>x=5:2\)
\(=> x=\frac{5}{2}\).Vậy \(x=\frac{5}{2}\)
\(9)18:x-5.2=8\)
\(=> 18:x-10=8\)
\(=>18:x=8+10\)
\(=>18:x=18\)
\(=> x=1\).Vậy \(x=1\)
\(10)5.5-2:x=24\)
\(=>25-2:x=24\)
\(=> 2:x=25-24\)
\(=>2:x=1\)
\(=>x=2\).Vậy \(x=2\)
Tính A=1/1×2×3+1/2×3×4+....+1/23×24×25
A = \(\frac{1}{1.2.3}+\frac{1}{2.3.4}+...+\frac{1}{23.24.25}\)
= \(\frac{1}{2}.\left(\frac{2}{1.2.3}+\frac{2}{2.3.4}+...+\frac{2}{23.24.25}\right)\)
= \(\frac{1}{2}.\left(\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+...+\frac{1}{23.24}-\frac{1}{24.25}\right)\)
= \(\frac{1}{2}\left(\frac{1}{1.2}-\frac{1}{24.25}\right)=\frac{1}{2}\left(\frac{1}{2}-\frac{1}{600}\right)=\frac{1}{2}.\frac{299}{600}=\frac{299}{1200}\)
C=1/1*2*3+1/2*3*4+...+1/23*24*25
\(C=\frac{1}{1.2.3}+\frac{1}{2.3.4}+...+\frac{1}{23.24.25}\)
\(=\frac{1}{2}\left(\frac{2}{1.2.3}+\frac{2}{2.3.4}+...+\frac{2}{23.24.25}\right)\)
\(=\frac{1}{2}\left(\frac{1}{1.2}-\frac{1}{2.3}+\frac{1}{2.3}-\frac{1}{3.4}+...+\frac{1}{23.24}-\frac{1}{24.25}\right)=\frac{1}{2}\left(\frac{1}{1.2}-\frac{1}{24.25}\right)=\frac{1}{2}.\frac{299}{600}=\frac{299}{1200}\)
789+456+123+786+0+96+96+852565=