Which term of AP 81, 77, 73, 69, is first negative term - Maths - Arithmetic Progressions

Question

Which term of AP 81, 77, 73, 69, is first negative term?

Varun.Rawat · Accepted Answer

We have,first term, a = 81common difference, d = 77-81 = -4Let an < 0⇒a+n-1d <0⇒81+n-1-4 < 0⇒-4n+4 < -81⇒-4n < -85⇒4n > 85⇒n > 21 25So, 22th term is the first negative term

Which term of AP 81, 77, 73, 69,...... is first negative term?