A) 1×5+5×9+9×13+...89×93+93×97
B) 1×3+3×5+5×7+....95×97+97×99
C) 1×3+5×7+9×11+..93×95+97×99
S = 99 – 97 + 95 – 93 + 91 – 89 + ….+11 – 9 + 7 – 5 + 3 – 1S = 99 – 97 + 95 – 93 + 91 – 89 + ….+11 – 9 + 7 – 5 + 3 – 1
99-97+95-93+91-89+...+7-5+3-1 = ?
50-49+48-47+46-45+...+4-6+2-1 = ?
Bài 2 : Tinh nhanh :
a, 2+4+6+8+...+100
b, 99-97+95-93+91-89+...+7-5+3-1
Tính tổng
a) 2+4+6+8+...+100
b) 99-97+95-93+91-89+...+7-5+3-1
a) 99-97+95-93+91-89+ ..... +7-5+3-1
b) 50-49+48-47+46-45+.....+4-3+2-1
Thực hiện phép tính theo cách hợp lí:
a)99-97+95-93+91-89+...+7-5+3-1
b)(125.37.32):4
c)A=5+8+11+14+...+302
a) 99 - 97 + 95 - 93 + 91 - 89 +...+ 7 - 5 + 3 - 1
b) 4 + 8 + 12 + 16 +...104
c) (37.93 - 17.93) : 93 + 23.0
(Bn nào ghi đc cách làm mk tick liền tay nha!!!!!!!!!!!!!!!!!)
99−97+95−93+91−89+⋯+7−5+3−1
99-97+95-93+91-89+......+7-5+3-1