Question

Find the value of a and b such that 18,a,b,-3 are in an AP
......Plz answer ASAP......
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Answer 1

Given that 18, a, b, -3 are in A.P

(a1=18, a2=a, a3=b, a4=-3)

Let 'd' be the common difference of A.P

a1 = 18

a4 = -3

∴a1 + 3d = -3

 d = -21/3 = -7

So, a2 - a1 = d

      a2 - 18 = -7

       a = -7 + 18  (a2=a)

      a = 11

Also, a4 - a3 = d

         -3 - a3 = -7

        -3 + 7 = b (a3=b)

          b = 4