Verified answer

[tex]Formula \: Used \: so \: \: that's \: \\ why \: \sqrt{3} \: is \: taken \\ \\ (a - b) {}^{2} = {a}^{2} + {b}^{2} - 2ab[/tex]

[tex]= ( \sqrt{5} - \sqrt{3} ) {}^{2} \\ \\ = ( \sqrt{5} ){}^{2} + ( \sqrt{3} ) {}^{2} - 2 \times \sqrt{5} \times \sqrt{3} \\ \\ = 5 + 3 + 2 \sqrt{15} \\ \\ = 8 + \sqrt{15} [/tex]

Answer:

Because here we have used formula

(a-b)² = a²-2ab+b²

That's why at the place of a there is √5 and at place of b there is √3