Bài 1.

\(B=1+2+3+\cdot\cdot\cdot+98+99\)

Số các số hạng trong \(B\) là:

\(\left(99-1\right):1+1=99\left(số\right)\)

Tổng \(B\) bằng: \(\left(99+1\right)\cdot99:2=4950\)

Bài 2.

\(A=1+3+5+\cdot\cdot\cdot+997+999\)

Số các số hạng trong \(A\) là:

\(\left(999-1\right):2+1=500\left(số\right)\)

Tổng \(A\) bằng: \(\left(999+1\right)\cdot500:2=250000\)

Bài 3.

\(C=2+4+6+\cdot\cdot\cdot+96+98\)

Số các số hạng trong \(C\) là:

\(\left(98-2\right):2+1=49\left(số\right)\)

Tổng \(C\) bằng: \(\left(98+2\right)\cdot49:2=2450\)

#\(Toru\)

Dãy số trên có số số hạng là:

(100-2):2+1=50(số số hạng)

Tổng của dãy số là:

(100+2)x50:2=2550

Đáp số: 2550

k mình nha

Chúc các bạn học giỏi nhé

có số số hạng là:

(100-2):2+1=50

=> tổng là:

(100+2).50:2=2800

Đáp số: 2 800

theo mk là 2550

ok chưa?

Ở đây:

Tham khảo nhé:          

http://olm.vn/hoi-dap/question/743551.html

Bạn có thể tham khảo:

http://olm.vn/hoi-dap/question/743551.html

= 1/2 -1/4 + 1/4 - 1/6 + 1/6 + 1/8 + ... + 1/96 - 1/98 + 1/98 - 1/100
= 1/2 - 1/100
= 49/10

\(S=\left(1-2\right)+\left(3-4\right)+...+\left(99-100\right)+101\)

\(=-1.50+101\)

\(=51\)

Số số hạng là :

(100−1):1+1=50( số hạng )

Tổng:

1−2+3−4+5−6+...+97−98+99−100+101

=(1−2)+(3−4)+(5−6)+...+(97−98)+(99−100)+101

=(−1)+(−1)+(−1)+...+(−1)+(−1)+101

=(−1)·50+101

=(−50)+101

=51

Tk mình với bạn ơi. Đúng rồi nhé!!

CHÚC BẠN HỌC TỐT ✓✓

\(S=1-2+3-4+5-6+...-98+99-100+101\)

\(S=\left(1-2\right)+\left(3-4\right)+\left(4-5\right)+...+\left(99-100\right)+101\)

\(S=-1\cdot50+101\)

\(S=-50+101\)

\(S=51\)

=(1+98-99-100)+(2-3-4+5)+(6-7-8+9)+...+(95-96-97+98)

=-100+0+0+0+0+0.........................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................................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C7: A

C8:A

C9:D

A. -1;-3;-89;-98

A. 6

D. 6

~hok tốt