Question


Given that p and q are the roots of the equation x2 – ax +b =0 and Dn= pn+qn. Find the value of Dn+1


Options:
A .   aDn- bDn-1
B .   aDn
C .   bDn
D .   aDn+ bDn-1
E .   pDn
Answer: Option A
:
A

Option (a)

Shortcut: Assumption

Assume a quadratic equation. Let’s take x2+5x-6=0.

Thus, a = sum of roots = -5 and b= product of roots = -6

Roots are p = 1 and q=-6

D1= p1+q1 = -5

D0 = 2

D2 = 37

Assume n=1

We need to find Dn+1 = D2 = 37

Look in the answer options for 37

Option a is the only one which gives (-5)(-5)-(-6)(2) = 37



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