Question

How to find the rationalising factor of 7-3√5

Answer 1

(7-3√5 ) × (7+3√5) = (7²-(3√5)²)
= 49- 45
= 4
here you go....hope this helps

Answer 2

Given:

The number 7-3√5

To find:

The rationalising factor of 7-3√5

Calculation:

Rationalising factor : If the product of two surds is a rational number, then each of them is called as a rationalising factor

Let ‘x’ be the rationalising factor of 7-3√5

=> (7-3√5)(x) = Rational number

Suppose x = 7+3√5, then we get

=>  (7-3√5)(7+3√5) = 49-9(5)

                               = 49-45

                               = 4

4 is a rational number. Therefore 7+3√5 is a rationalising factor

Final answer:

The rationalising factor of 7-3√5 is 7+3√5