Q.
Let α1,β1 are the roots of x2−6x+p=0 and α2,β2 are the roots of x2−54x+q=0. If α1,β1,α2,β2 form an increasing G.P., then find the value of (q−p).
Let α1=A,β1=AR,α2=AR2,β2=AR3 we have α1+β1=6⇒A(1+R)=6....(1) α1β1=p⇒A2R=p....(2)
Also α2+β2=54⇒AR2(1+R)=54....(3) α2β2=qA2R5=q....(4)
Now, on dividing equation (3) by equation (1), we get A(1+R)AR2(1+R)=654=9 ⇒R2=9 ∴R=3 (As it is an increasing G.P.) ∴ On putting R=3 in equation (1) A=46=23 ∴p=A2R=49×3=427 and q=A2R5=49×243=42187 Hence q−p=42187−27=42160=540