2-1+3-2+4-3+……+50-49+51-50
2-1+3-2+4-3+……+50-49+51-50
1*2+2*3+3*4+……+50*51
奥数题1+2+3+4+……+49+50
求1/2+(3/1+2/3)+(1/4+2/4+3/4)+……+(1/50+2/50+3/50+……+48/50+49/
1*2+2*3+3*4+4*5+5*6+……48*49+49*50
巧算:50-49+48-47+…+4-3+2-1
1+2+3+……48+49+50+49+48+……+3+2+1
1/1×3+1/3×5+1/5×7+…………+1/49×51和1/2×4+1/4×6+1/6×8+…………1/48×50
1/2×3+1/3×4+1/4×5+……+1/49×50
1*2+2*3+3*4+…+48*49+49*50
5/(2*1)+5/(2*3)+5/(3*4)……5/(49*50)等于多少
1×2×3分之一+2×3×4分之一……+48×49×50分之一咋算