Các câu hỏi tương tự
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
A=99-97+95-93+91-89+....+7-5+3-1=?
A = 99 -97 + 95 - 93 + 91 - 89 + … + 7 - 5 + 3 - 1
A = 99 -97 + 95 - 93 + 91 - 89 + … + 7 - 5 + 3 – 1
99−97+95−93+91−89+⋯+7−5+3−1
99-97+95-93+91-89+......+7-5+3-1
Bài 9: Tính nhanh
a) 99 - 97 + 95 - 93 + 91 - 89 + ..... + 7 - 5 + 3 - 1
b) 50 - 49 + 48 - 47 + 46 - 45 + ..... + 4 - 3 + 2 -1
99-97+95-93+91-89+.......+7-5+3-1