Question

If x³ + 5x² + 25x – 1 = 0 then find x³ + 5/x
1. 126
2. 125
3. 162
4. 116

Answer 1

Correct Answer - Option 1 : 126

Given:

x³ + 5x² + 25x – 1 = 0

Calculation:

Considering the given equation

x³ + 5x² + 25x – 1 = 0

x³ + 5x² + 25x = 1      ----(1)

Dividing equation 1 by x

x² + 5x + 25 = 1/x

Now,

x³ + 5/x

⇒ x³ + 5(x² + 5x + 25 )

⇒ x³ + 5x² + 25x + 125

From equation (1)

⇒ 1 + 125

⇒ 126