The sum of square of two numbers X and Y is 85 and multiplication is 42. If X >Y then value of X-Y will be.

Given:
​$$X^2 + Y^2 = 85$$​​
​$$X \times Y = 42$$​​
X > Y

Formula Used:
​​​$$(a - b)^2 = a^2 + b^2 - 2ab$$

Using $$(X - Y)^2 = X^2 + Y^2 - 2XY :$$​​
$$(X - Y)^2$$​ = 85 - 2(42) = 85 - 84 = 1

​$$(X - Y) = \sqrt{1}$$

(X - Y) = 1

Thus, the correct answer is (d).