Question

If 18,a,b,-3 are in ap then find a+b

Answer 1

Answer:

Let p, be the first term i.e; 18

And, d, be the common difference,

From given series,

4th term =p+3d=−3

⟹18+3d=−3

Hence, d=−7

So, a=p+d=18−7=11

And, b=p+2d=18−14=4

Therefore,

a+b=11+4=15

Answer 2

Answer:

$18 \: \: a \: \: b \: \: - 3 \: \: are \: in \: ap \\ a - 18 = - 3 - b \\ a + b = - 3 + 18 \\ a + b = 15$