The sum of odd sequence of arithmetic sequence is 51, the sum of even sequence is 42 and half, the first term is 1, and the number of terms is odd. Find the formula of the last term and the general term of this sequence

The sum of odd sequence of arithmetic sequence is 51, the sum of even sequence is 42 and half, the first term is 1, and the number of terms is odd. Find the formula of the last term and the general term of this sequence

Let the last term be a, the number of terms be n, and the tolerance be d
(a+1)n/2=51+42.5
(a+1)(n+1)/2/2=51
The solution is a = 16, n = 11
Substituting a = 1 + (n-1) d
The result is d = 1.5
So the last term of this sequence is 16, and the general formula is a = 1 + (n-1) * 1.5

1+2+3+4+…… +What is 48 + 49 + 50?
Make a list of fank

Sum according to Gauss: SN = [n * (n + 1)] / 2 (SN: sum of the first n terms)
If n = 50
Sn=1275
Again, have you heard the story of Gauss?

12.5 * 88.8-0.25 * 4.44 simple operation
No, the answer is 1108.89

12.5*88.8-0.25*4.44
=12.5*8*11.1-0.25*4*1.11
=100*11.1-1*1.11
=1110-1.11
=1108.89

Group summation of sequence
1+(1+3)+(1+3+3²）+（1+3+3²+3³）+···+[1+3+3²···+3^(n-1)]=

1+(1+3)+(1+3+3²）+（1+3+3²+3³）+···+[1+3+3²···+3^(n-1)]
=(3-1)/2+(3^2-1)/2+(3^3-1)/2+.+(3^n-1)/2
=(1/2)*[3+3^2+...+3^n]-(1/2)*n
=(1/2)*3*(3^n-1)/(3-1)-n/2
=(3/4)*(3^n-1)-n/2
=(1/4)*3^(n+1)-n/2-3/4

Urgent! Monotone increasing interval monotone decreasing interval of function f (x) = | 2x-1 | + | 2x + 2 |

When x is not greater than - 1, y = - 4x - 1, when x is greater than - 1 and less than 1 / 2, y = 3, when x is not less than 1 / 2, y = 4x + 1, so the decreasing interval of the function is (negative infinity, - 1), and the increasing interval is [1 / 2, positive infinity]

Finding the greatest common factor and the least common multiple of 48, 72 and 120

The greatest common factor of 48, 72 and 120 is 24, and the least common multiple is 720

a÷______ =B & nbsp; (neither a nor B is 0)

A △ B = & nbsp; a & nbsp; B (neither a nor B is 0), so the answer is: & nbsp; a & nbsp; B

Finding the derivative of y = e ^ - 3x ^ 2

e^(-3x^2)*(-3x*2)=-6xe^(-3x^2)

Simple operation of multiplying 5 / 99 and 16 by negative 8

99 and 5 / 16 times minus 8
=(100-11/16)×(-8)
=-800+11/2
=-800+5+1/2
=-794-6+5+1/2
=-794-1/2
=-794 1 / 2

What is the quotient of the sum of 2 / 7 and its reciprocal minus the difference between 3 and 0.1?
I'm in a hurry. I'm in a hurry

Analysis: the reciprocal of 2 out of 7 is 7 out of 2, then: the sum of 2 out of 7 and its reciprocal is equal to 2 out of 7 + 2 out of 7 = 14 (4 + 49) = 14 53, and the difference between 3 and 0.1 is equal to 2.9