Question

If 4x² - 40x + 10 = 0, then the value of x² - 10x + 5 equals to:
1. 2.5
2. 1.5
3. 0
4. -2.5

Answer 1

Correct Answer - Option 1 : 2.5

Given:

4x² - 40x + 10 = 0

Calculation:

4x² - 40x + 10 = 0

⇒ 4x² - 40x = - 10 

⇒ x² - 10x = - 10/ 4 = - 2.5      ----(1)

Put the value of x² - 10x in the x² - 10x + 5 get,

x2 - 10x + 5 = - 2.5 + 5 = 2.5      [Using (1)]

∴ The required value of x2 - 10x + 5 is 2.5.