Question

cum se afla :
(2radical din 5+1) totul la a 2

Answer 1

(2√5+1)²= ((2√5+1)(2√5+1)
 
             =4·5+ 2√5+ 2√5+ 1
 
             = 20+ 4√5+ 1
 
             =21+ 4√5

Answer 2

$(2\sqrt5+1)^2=(2\sqrt5)^2+2 \cdot 2\sqrt5 \cdot 1+1^2=2^2\sqrt5^2+4\sqrt5+1=\\= 4 \cdot5+4\sqrt5+1=20+4\sqrt5+1= \boxed{\bold{4\sqrt5+21}};$