Question

97. If x = (2-13), then the value of
x3 - 2x2 - 7x + 5 is
(1) 2
(3) O
(2) 1
(4) 3
T
03​

Answer 1

Answer:

Solution:-

x=2−31

Multiplying the numerator and denominator by the conjugate of the denominator, we have

x=2−31×2+32+3=22−322+3=4−32+3=2+3

⇒x2=(2+3)2=4+43+3=7+43

Now consider the given expression

x3−2x2−7x+5=x3−7x−2x2+5

⇒=x(x