Tính M: M = 3/(2 * 5) + 3/(5 * 8) + 3/(8 * 11) + 3/(11 * 14) +....+ 3/(98 * 101)

To find the sum of the series, we need to first identify the pattern in the terms.

The general term of the series can be written as:

Tn = 3/(3n-1)x(3n+2)

Now, we need to find the sum of the series up to n=98.

S98 = Σ(3/(3n-1)x(3n+2)) from n=1 to 98

S98 = 3/(3(1)-1)x(3(1)+2) + 3/(3(2)-1)x(3(2)+2) + ... + 3/(3(98)-1)x(3(98)+2)

S98 = 3/2x5 + 3/5x8 + 3/8x11 + ... + 3/293x296

To find the sum of the series, we can use the formula for the sum of an arithmetic series:

Sn = n/2 x (first term + last term)

S98 = 98/2 x (5 + 296)

S98 = 49 x 301

S98 = 14949

Therefore, the sum of the series up to n=98 is 14949.