Question

How many terms of the AP -6,-11/2,-5,.... make the sum -25

Answer 1

Answer:

CORRECT ANSWER IS

Explanation:

a=-6

d=-11/2-(-6)

=-11+12/2

=1/2

Sn=-25

Now,

Sn=n/2(2a+(n-1)d)

-25=n/2(2(-6)+1/2n-1/2)

-25=n/2(-24+1n-1/2)

-25×2=n(-25+1n)

-50=-25n+n²

0=n²-25n+50 Ans

Further do middle term splitting and 2 answers will come one negative and one positive eliminate the negative answer and the positive answer is the correct answer because no.of terms can never be negative. Thank you!hope it helps