Question

Find a and b such that 9,a,b and 3 are in AP.

Answer 1

A - 9 = B - A = 3 - B(common difference)...

SO, A = 7 and B = 5...

Hope it helped you a lot....

Answer 2

let d be the common difference
first term=9
fourth term=3
n=4
or first term+(n-1)d=3
or 9+(4-1)d=3
or 9+3d=3
or 3d=3-9
or 3d=-6
or d=-2
thus a-9=-2
or a=-2+9
or a=7

b-a=-2
or b=-2+7
or b=5
thus a=7 and b=5