4/3x9/8x16/15x25/24x36/35x49/48x64/63x81/80x100/99x121/120
9/8x16/15x25/24x36/35x49/48x64/63x81/80=?
cac bạn giúp mik với
\(\frac{9}{8}\)x \(\frac{16}{15}\)x \(\frac{25}{24}\)x \(\frac{36}{35}\)x\(\frac{49}{48}\)x\(\frac{64}{63}\)x\(\frac{81}{80}\)
= \(\frac{3x3}{2x4}\)x \(\frac{4x4}{3x5}\)x\(\frac{5x5}{4x6}\)x\(\frac{6x6}{5x7}\)x\(\frac{7x7}{6x8}\)x\(\frac{8x8}{7x9}\)x\(\frac{9x9}{8x10}\)
= \(\frac{3x3x4x4x5x5x6x6x7x7x8x8x9x9}{2x4x3x5x4x6x5x7x6x8x7x9x8x10}\)
= \(\frac{3x9}{2x10}\)
= \(\frac{27}{20}\)
Tính nhanh:
4/3x9/8x16/15x25/24x29/30x....x10000/9999.
Các bạn làm ơn giúp mik vs.ai nhanh mik tick cho nha.thank you very much
4/3x9/8x16/15x...x3481/3480
\(\frac{4}{3}.\frac{9}{8}.\frac{16}{15}.....\frac{3481}{3480}\)
\(=\frac{2^2}{1.3}.\frac{3^2}{2.4}.\frac{4^2}{3.5}....\frac{59^2}{58.60}\)
\(=\frac{2.3.4.....59}{1.2.3.....58}.\frac{2.3.4....59}{3.4.5....60}\)
\(=59.\frac{2}{60}=\frac{59}{30}\)
Ta có : \(\frac{4}{3}.\frac{9}{8}.\frac{16}{15}.......\frac{3481}{3480}\)
\(=\frac{2.2}{1.3}.\frac{3.3}{2.4}.\frac{4.4}{3.5}........\frac{59.59}{58.60}\)
\(=\frac{2.3.4........59}{1.2.3.......58}.\frac{2.3.4.......59}{3.4.5........60}\)
\(=59.\frac{1}{30}=\frac{59}{30}\)
Tính Nhanh : 4/3x9/8x16/15x...x9801/9800
Ta phân tích: 4/3=2/1x2/3;9/8=3/2x3/4;16/15=4/3x4/5;.......;99/98x99/100, Ta có dãy số:2/1x2/3x3/2x3/4x4/3x4/5x........x99/98x99/100. Xóa bớt những tử số và mẫu số giống nhau, ta có kết quả bằng: 2/1x99/100= 2x99/100=99/50
Tính A, biết :
A=4/3x9/8x16/15x...x400/399 ( sử dụng phương pháp giải lớp 6 nha)
A = \(\dfrac{4}{3}\) \(\times\) \(\dfrac{9}{8}\) \(\times\) \(\dfrac{16}{15}\) \(\times\) ....... \(\times\) \(\dfrac{400}{399}\)
Đặt tử số là B; mẫu số là C ta có:
B = 4 \(\times\) 9 \(\times\) 16 \(\times\).....\(\times\) 400
B = 22 \(\times\) 32 \(\times\) 42 \(\times\) ......\(\times\) 202
B = 22 \(\times\)( 3 \(\times\) 4 \(\times\) .......\(\times\) 19)2 \(\times\) 202
C = 3 \(\times\) 8 \(\times\) 15 \(\times\) ......\(\times\) 339
3 = 1 \(\times\) 3
8 = 2 \(\times\) 4
15 = 3 \(\times\) 5
..........................
399 = 19 \(\times\) 21
Nhân vế với vết ta được:
C = 1 \(\times\) 2 \(\times\) 3 \(\times\) 4\(\times\)....\(\times\)19\(\times\)3 \(\times\) 4 \(\times\) 5 \(\times\).....\(\times\)21
C = 1 \(\times\) 2 \(\times\)( 3 \(\times\) 4 \(\times\).....\(\times\) 19)2 \(\times\) 20 \(\times\) 21
A = \(\dfrac{2^2\times\left(3\times4\times...\times19\right)^2\times20^2}{1\times2\times\left(3\times4\times....\times19\right)^2\times20\times21}\)
A = \(\dfrac{2\times\left(3\times4\times...\times19\right)^2\times20}{2\times\left(3\times4\times...\times19\right)^2\times20}\) \(\times\) \(\dfrac{2\times20}{1\times21}\)
A = 1 \(\times\) \(\dfrac{40}{21}\)
A = \(\dfrac{40}{21}\)
9x5^20x27^9-3x9^15x25^9:7x3^29x125^26-3x3^9x15^19
9x5^20x27^9-3x9^15x25^9:7x3^29x125^26-3x3^9x15^19
x5^20x27^9-3x9^15x25^9/7x3^29x125^6-3x3^9x15^19
\(\frac{1}{3x9}+\frac{1}{9x15}+\frac{1}{15x25}+...+\frac{1}{39x45}\)
Ai làm được thì tui tk cho!
Gọi biểu thức trên là A ta có :
6A\(=\frac{6}{3x9}+\frac{6}{9x15}+\frac{6}{15x25}+....+\frac{6}{39x45}\)
\(=\frac{1}{3}-\frac{1}{9}+\frac{1}{9}-\frac{1}{15}+\frac{1}{15}-\frac{1}{25}+....+\frac{1}{39}-\frac{1}{45}\)
\(=\frac{1}{3}-\frac{1}{45}=\frac{14}{45}\)
\(\Rightarrow A=\frac{14}{45}:6=\frac{7}{135}\)