Let , be the roots of the equation x2-ax-b=0 with Im( )<Im( ). Let Pn= n- n. If P3=-5 7 i, P4=-3 7 i, P5=11 7 i and P6=45 7 i, then | 4+ 4 | is equal to .
Answer
31
Solution
tn+2=atn+1+btn Pn+2=aPn+1+bPn. Using P5,P6: 3a+5b=-11 and 11a-3b=45 a=3, b=-4.
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x2-3x+4=0: + =3, =4 2+ 2=1
4+ 4=1-2(16)=-31
| 4+ 4|=31
Answer: 31