Question

The value of the expression 1-6+2-7+3-8+.........to 100 terms is

Answer 1

(1+2+3+...50 terms)-(6+7+8...50 terms) ------------ equation 
so now these are in ap
for (1+2+3+...50 terms) n=50, a=1 and d=1
by the formula Sn = n/2(2a+(n-1)d)
                             =50/2(2(1)+(50-1)1)
                              =25(51) ---------------------- 1
similarly for (6+7+8...50 terms) n=50, a=6, d=1
by placing this in formula we get 50/2(2(6)+(50-1)1)
                                               = 25(12+49)
                                               = 25(61) --------2
by adding 1 and 2 we get the value by the equation formed at first
                      = 25(51)-25(61)
                      = 25(51-61)
                      = 25(-10)
                      = -250
therefore, the value of given expression is -250
                              

Answer 2

Answer:

the correct answer is

Step-by-step explanation:

-250