Q. What is the 1st negative term of the A.P. 17, 15, 13,.... ( With full solution plz ).
Answers
Answered by
0
The common difference of this arithmetic
progression is -2, then
72 (n/2) * (2a+ (n-1)d), where a is the first term,
n is the number of terms and d is the common
difference
72 (n/2) (217) + (n-1-2))
72 (n/2)*(34-2n +2)
144 n (34-2n+ 2)
144 36n -2n^2
2n^2-36n +144 0
n2-18n +72 = 0
(n-12) "(n-6)= 0
hope it helps you
Answered by
1
Answer:
first term = 17
common difference = 15-17= -2
an should be less than 0 because we are finding negative term which are less than 0
an <0
a+(n-1) d < 0
17+(n-1)(-2)<0
17-2n+2<0
19-2n<0
n=19/2
=9.5
so, the first negative term is 10
let's check our answer
by putting the value of n=10
a+(n-1) d
17+(10-1)(-2)
17+9(-2)
17-18
-1
so, you get first negative no.
hope you understand..❤thanks
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