Question

7/8x12/11-3/8x11/12怎么算？

Answer 1

3/(2x5)+3/(5x8)+3/(8x11)+...+3/(1999x2002)+1/2002=(1/2-1/5)+(1/5- 1/8 )+(1/8-1/11)+...+(1/1999-1/2002)+1/2002=1/2-1/5+1/5-1/ 8+1/8- 1/11+...+1/1999-1/2002+1/2002=1/2-1/2002+1/2002=1/2①例如：3/(2x5)+3/(5x8)+3 /(8x11)+...+3/(20x23)=(1/2-1/5)+(1/5-1/8)+(1/ 8-1/11)+...+( 1/20-1/23)=1/2-1/5+1/5-1/8+1/8-1/11+.. ....+1/20-1/23=1/ 2-1/23=21/46 ②例如：1/(2x5)+1/(5x8)+1/(8x11)+1/(11x14) =1/3x[3/(2x5)+3/(5x8) )+3/(8x11)+3/(11x14)]=1/3x[(1/2-1/5)+(1/5-1 /8)+(1/8-1/11)+( 1/11-1/14)]=1/3x(1/2-1/5+1/5-1/8+1/8-1 /11+1/11-1/14)=1/3x (1/2-1/14)=1/3x(7/14-1/14)=1/3x6/14=1/3x3/7= 1/7 2*3/5=1/2-1/ 55*3/8=1/5-1/8....1999*3/2002=1/1999-1/2002 所以 2 *3/5+5*3/8+8*3/11.. .+1999*3/2002+1/2002=1/2

Answer 2

3/2x5+3/5x8+3/8x11+3/11x14+3/14x17+3/17x20
= (1/2-1/5)+(1/5-1/8)+(1/8-1/11)+...+(1/17-1/20)
= 1/2 - 1/20
= 9/20

Answer 3

3/2x5+3/5x8+3/8x11+3/11x14+3/14x17+3/17x20
= (1/2-1/5)+(1/5-1/8)+(1/8-1/11)+...+(1/17-1/20)
= 1/2 - 1/20
= 9/20

Answer 4

3/2x5+3/5x8+3/8x11+3/11x14+3/14x17+3/17x20
= (1/2-1/5)+(1/5-1/8)+(1/8-1/11)+...+(1/17-1/20)
= 1/2 - 1/20
= 9/20

Answer 5

3/2x5+3/5x8+3/8x11+3/11x14+3/14x17+3/17x20
= (1/2-1/5)+(1/5-1/8)+(1/8-1/11)+...+(1/17-1/20)
= 1/2 - 1/20
= 9/20