Which term of the A.P -18, -16, -14, …………………. is first p

1.	Which term of the A.P -18, -16, -14, …………………. is first positive term ? A) t9B) t10C) t11D) t12
Answer» Correct option is (C) t₁₁ Given A.P. is -18, -16, -14, …..... \(\because a_1=-18,a_2=-16\) \(d=a_2-a_1\) = -16 - (-18) = -16+18 = 2 \(\because t_n=a+(n-1)d\) \((\because a_1=a)\) First positive term in given A.P. is 2. \(\therefore2=-18+(n-1)(2)\) \(\Rightarrow2+18=2(n-1)\) \(\Rightarrow n-1=\frac{20}2=10\) \(\Rightarrow n=10+1=11\) Hence, \(11^{th}\) term of A.P. is first positive term. Correct option is C) t₁₁

Which term of the A.P -18, -16, -14, …………………. is first positive term ? A) t9B) t10C) t11D) t12

Answer»

Correct option is (C) t₁₁

Given A.P. is -18, -16, -14, ….....

\(\because a_1=-18,a_2=-16\)

\(d=a_2-a_1\)

= -16 - (-18)

= -16+18 = 2

\(\because t_n=a+(n-1)d\) \((\because a_1=a)\)

First positive term in given A.P. is 2.

\(\therefore2=-18+(n-1)(2)\)

\(\Rightarrow2+18=2(n-1)\)

\(\Rightarrow n-1=\frac{20}2=10\)

\(\Rightarrow n=10+1=11\)

Hence, \(11^{th}\) term of A.P. is first positive term.

Correct option is C) t₁₁