Tổng: 1 + 2x2 + 3x3 + 4x4 + 5x5 + 6x6 + 7x7 + 8x8 + 9x9 + 10x10 là bao nhiêu?
1x1=
2x2=
3x3=
4x4=
5x5=
6x6=
7x7=
8x8=
9x9=
10x10=
1 x 1 = 1
2 x 2 = 4
3 x 3 = 9
4 x 4 = 16
5 x 5 = 25
6 x 6 = 36
7 x 7 = 49
8 x 8 = 64
9 x 9 = 81
10 x 10 = 100
\(1x1=1\)
\(2x2=4\)
\(3x3=9\)
\(4x4=16\)
\(5x5=25\)
\(6x6=36\)
\(7x7=49\)
\(8x8=64\)
\(9x9=81\)
\(10x10=100\)
1 x 1 = 1
2 x 2 = 4
3 x 3 = 9
4 x 4 = 16
5 x 5 = 25
6 x 6 = 36
7 x 7 = 49
8 x 8 = 64
9 x 9 = 81
10 x 10 = 100
1x1=
2x2=
3x3=
4x4=
5x5=
6x6=
7x7=
8x8=
9x9=
10x10=
11x11=
12x12=
13x13=
14x14=
15x15=
16x16=
17x17=
18x18=
19x19=
20x20=
ai đúng mình tích
1x1=1
2x2=4
3x3=9
4x4=16
5x5=25
6x6=36
7x7=49
8x8=64
9x9=81
10x10=100
11x11=121
12x12=144
13x13=169
14x14=196
15x15=225
16x16=256
17x17=289
18x18=324
19x19=361
20x20=400
Tính bằng cách thuận tiện nhất:
1/2x2/3x3/4x4/5x5/6x6/7x7/8x8/9
So sánh số sau: 1/2x2+1/3x3+1/4x4+1/5x5+1/6x6+1/7x7+1/8x8 với 1.
đặt \(A=\frac{1}{2.2}+\frac{1}{3.3}+\frac{1}{4.4}+\frac{1}{5.5}+\frac{1}{6.6}+\frac{1}{7.7}+\frac{1}{8.8}=\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+\frac{1}{5^2}+\frac{1}{6^2}+\frac{1}{7^2}+\frac{1}{8^2}\)
\(A
Chứng tỏ rằng
B=\(\frac{1}{2x2}+\frac{1}{3x3}+\frac{1}{4x4}+\frac{1}{5x5}+\frac{1}{6x6}+\frac{1}{7x7}+\frac{1}{8x8}< 1\)
Ta thấy:
1/2*2<1/1*2)vì 2*2>1*2).
1/3*3<1/2*3(vì 3*3>2*3).
...
1/8*8<1/7*8(vì 8*8>7*8).
=>1/2*2+1/3*3+1/4*4+...+1/8*8<1/1*2+1/2*3+1/3*4+...+1/7*8.
=>B<1-1/2+1/2-1/3+1/3-1/4+1/4-1/5+1/5-1/6+1/6-1/7+1/7-1/8.
=>B<1-1/8.
=>B<7/8.
Mà 7/8<1.
=>B<1.
Vậy B<1(đpcm).
\(< \frac{1}{1\cdot2}+\frac{1}{2\cdot3}+\frac{1}{3\cdot4}+\frac{1}{4\cdot5}+\frac{1}{5\cdot6}+\frac{1}{6\cdot7}+\frac{1}{7\cdot8}\)
\(\Rightarrow1-\frac{1}{8}< 1\)
=>B<1
\(B=\frac{1}{2.2}+\frac{1}{3.3}+\frac{1}{4.4}+\frac{1}{5.5}+\frac{1}{6.6.}+\frac{1}{7.7}+\frac{1}{8.8}\)\(=\)\(\frac{1}{2^2}+\frac{1}{3^2}+\frac{1}{4^2}+\frac{1}{5^2}+\frac{1}{6^2}+\frac{1}{7^2}+\frac{1}{8^2}\)
\(B=\frac{1}{1.2}+\frac{1}{2.3}+\frac{1}{3.4}+\frac{1}{4.5}+\frac{1}{5.6}+\frac{1}{6.7}+\frac{1}{7.8}\)
\(B=1-\frac{1}{2}+\frac{1}{2}-\frac{1}{3}+\frac{1}{3}-\frac{1}{4}+\frac{1}{4}-\frac{1}{5}+...+\frac{1}{7}-\frac{1}{8}\)
\(B=1-\frac{1}{8}\)
\(\Rightarrow B< 1\left(ĐPCM\right)\)
cho mình hỏi là bài tính nhanh 1/2x2/3x3/4x4/5x5/6x6/7x7/8 làm như thế nào ạ
1x1= 6x6=
2x2= 7x7=
3x3= 8x8=
4x4= 9x9=
5x5= 10x10=
1x1=1 6x6=36
2x2=4 7x7=49
3x3=9 8x8=64
4x4= 16 9x9=81
5x5=25 10x10=100
Tick mk vài cái cho lên 210 nha !!!
1x1=2
2x2=4
3x3=9
4x4=16
5x5=25
6x6=36
7x7=49
8x8=64
9x9=81
10x10=100
E=1x1+3x3+5x5+7x7+...+25x25
F=4x4+7x7+10x10+...+19x19
giúp mik với thank các bn
E= 2925
F= 951
nho k cho minh nha minh dang can diem
E= 1x1+3x3+5x5+7x7+9x9+11x11+13x13+15x15+17x17+19x19+21x21+25x25=2925
F= 4x4+7x7+10x10+13x13+16x16+19x19=951
bai nhu vay day cho minh xin mot k nha ko co cung duoc
9x9=
8x8=
7x7=
6x6=
5x5
9 x 9 = 81
8 x 8 = 64
7 x 7 = 49
6 x 6 = 36
5 x 5 = 25
~~~~~hok tốt ~~~~~~!!!!###$$$$>>>>33333