S1=1-4+7-10+13-16+...+97-100
S1=(1+7+13+...+97)-(4+10+16+...+100)
S1=\(\frac{\left[\left(97-1\right):6+1\right].\left(97+1\right)}{2}-\frac{\left[\left(100-4\right):6+1\right].\left(100+4\right)}{2}\)
S1=\(\frac{17.98}{2}-\frac{17.104}{2}\)
S1=17.49-17.52
S1=17.(49-52)
S1=17.(-3)
S1=-51
Vậy S1=-51
-1+4-7+10-13+16-.....-97+100-103
Tính bằng cách thuận tiện nhất :
a, 1 - 2 + 3 - 4 + 5 - 6 + ... + 97 - 98 + 99 - 100 + 101
b, 10 - 12 + 14 - 16 + 18 - 20 + ... + 90 - 92 + 94 - 96 + 98
c, 1 - 4 + 7 - 10 + 13 - 16 + ... + 85 - 88 + 91 - 94 + 97
Tính:
a, (-1)+4-7+10-13+16-...-97+100+103
b, A= (-1)+2+22+23+24+25-...-298+299-2100.
Thu gọn
a. A=-(a-b+c)-(a+b-a)-(-c+d)
b. B=(-113+17-29)-(17-113-30)
c. C=1-4+7-10+13-16+...+97-100
5/4×7+5/7×10+5/10×13+........+5/97×100
6/4*7 + 6/7*10 + 6/10*13 +... + 6/97*100
a,-5+(-10)+(-15)+(-20)+.......+(-100)
b,-4+(-8)+(-12)+(-16)+.........+(-100)
c,1+(-3)5+(-7)+9+(-11)+.......+97+(-99)
(1-3/4)(1-3/7)(1-3/10)(1-3/13)....(1-3/97)(1-3/100) = ?
