Question

(5+ root 5) (5-roots).​

Answer 1

$\\ \sf Answer:- 20\\\\ \sf Formula \;used = (a+b)(a-b)=a^{2} -b^{2} \\\\\implies(5+\sqrt{5} )(5-\sqrt{5} )\\\\\implies5^{2} -(\sqrt{5} )^{2} \\\\\implies25-5\\\\\implies20$

Additional Information:-

$\implies(a+b)^{2} = a^{2} +b^{2} +2ab\\\\\implies(a-b)^{2} =a^{2} +b^{2} -2ab$

Answer 2

Answer:

20

Step-by-step explanation:

(5+√5)(5-√5) is in (a+b)(a-b) form.

$(a + b)(a - b) = {a}^{2} - {b}^{2}$

here it is

${5}^{2} - (\sqrt{5} ) {}^{2} = 25 - 5 = 20$