Question

5th term of an ap is 1 and 11th term is 17 what term of ap is 77

Answer 1

a + 4d = 1

a + 10d = -17;

setting the equations equal to each other you get:

a + 4d - 1 = 0; a + 10d + 17 = 0;

0=0 thus => a + 4d - 1 = a + 10d + 17

Solve:

-18 = 6d => -3 = d

using an existing equation and plugging in the known variables:

a + 4(-3) = 1 => a = 13


a + 10(-3) = -17 => a = 13

This shows that either equation can be used to get the answer**

solving the the xth (unknown) term by plugging in known variables:

a + xd = -77 => 13 + x(-3) = -77 => x(-3) = -90 => x = 30

So the 30th term of the AP is -77 or “a + 29d = -77”