Let p and q be roots of the equation x 2 - 2 x + A = 0 and let r and s be the roots of the equation x 2 - 18…

Let p and q be roots of the equation x2-2x+A=0 and let r and s be the roots of the equation x2-18x+B=0. If p<q<r<s are in AP, then A and B are
  1. -3,-77
  2. 3,-77
  3. -3,77
  4. 3,77

Solution

Let the four numbers in A.P. be

p=a-3d, q=a-d, r=a+d, s=a+3d.

Now, p and q are the roots of the quadratic equation x2-2x+A=0.

Therefore, using the sum and product of roots of a quadratic equation, we get

p+q=2   i

pq=A   ii

And, r,s are the roots of the quadratic equation x2-18x+B=0.

Therefore,

r+s=18   iii

rs=B   iv

By i and iii, we have

p+q+r+s=4a=20

a=5

Now,

p+q=2

10-4d=2

d=2.

Also, 

r+s=18

10+4d=18

d=2.

Hence, the numbers are -1, 3, 7, 11.

Therefore, pq=A=-3, rs=B=77.

Asked in: AP EAMCET 2021 (19 Aug Shift 2)

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