Question

If x=√5+1/2 , then find the valaue of 2x³+x²-5x+4.​

Answer 1

Answer:

Let the function be represented by f(x).

As x+2, exactly divides f(x), 

−2 is a zero of f(x), hence f(−2)=0

f(x)=2x3+5x2−x−k

f(−2)=2(−23)+5(−22)+2−k=0

⇒0=−16+20+2−k

⇒k=6

Answer 2

$x = \sqrt{5} + \frac{1}{2} = \frac{2 \sqrt{5} + 1}{2}$

so ,

$2 {x}^{3} + {x}^{2} - 5x + 4 = - 16$