1/1*3加1/3*5加.+1/49*51 *是乘法

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1/1*3加1/3*5加.+1/49*51 *是乘法

1/1*3加1/3*5加.+1/49*51 *是乘法
1/1*3加1/3*5加.+1/49*51 *是乘法

1/1*3加1/3*5加.+1/49*51 *是乘法
1/1*3+1/3*5+.+1/49*51
=(1-1/3)/2+(1/3-1/5)/2+(1/5-1/7)/2+(1/7-1/9)/2+.+(1/47-1/49)/2+(1/49-1/51)/2
=(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+.+1/47-1/49+1/49-1/51)/2
=(1-1/51)/2
=(50/51)/2
=25/51

1/1*3加1/3*5加............+1/49*51
=(1-1/3)/2+(1/3-1/5)/2+(1/5-1/7)/2+(1/7-1/9)/2+......+(1/49-1/51)/2
=(1-1/3+1/3-1/5+1/5-1/7+1/7-1/9+........+1/49-1/51)/2
=(1-1/51)/2
=(50/51)/2
=25/51

1/1*3加1/3*5加............+1/49*51
=1/2*(1-1/3+1/3-1/5+...+1/49-1/51)
=1/2*(1-1/51)
=50/102
=25/51