Question

IF a=5-2√5 , then find a²​

Answer 1

Answer:

45 is the correct answer.

solution:-

a=5-2√5

a=3√5

a^2

(3√5)^2

9×5

45 is the correct answer.

Answer 2

a= 5-2√5

a^2=?

$\sf\ \ a^2= \big(5-2\sqrt{5}\big)^2\\ \\ \\ \sf\ \ (a-b)^2= a^2+b^2-2ab\\ \\ \\ :\implies\sf\ \ a^2= (5)^2+(2\sqrt{5})^2-2\times 5\times 2\sqrt{5} \\ \\ \\ :\implies\sf\ 25+20-20\sqrt{5}\\ \\ \\ :\implies\sf\ 45-20\sqrt{5}$