Question

Solve root of 21-4root5+8root3-4root 15

Answer 1

Hey☺️

Expand :

(a+b√3+c√5) ^2

=(a^2+3b^2+5c^2) +2ab^3+2ac√5+2bc√15

coefficients equation needed:

ab=4, ac=-2, bc=-2.

Or

(a,b,c) = (2,2,-1) or (-2,-2,1)

= a^2 + 3b^2 + 5c^2 = 21.

$So \: the \: square \: root \: is \\ \\ \: 2 + 2 \sqrt{3} - 5$

♥️