4)
a) (√2+1-√2+1)/(√2-1)(√2+1)+(3√2-2√2)/6x2x6√2=2/(2-1)+√2x6√2/12=
2+12/12=2+1=3
b)
b=(√6)²=6
a=3
√a+b=√3+6=√9=3 (nr.natural)
5)
[(x²+3)-x]²=(x²+3)²-2x(x²+3)+x²=x⁴+6x²+9-2x³-6x+x²
(x²-x)²=x⁴-2x³+x²
E(x)=x⁴+6x²+9-2x³-6x+x²-x⁴+2x³-x²-5x²=x²-6x+9=(x-3)² (patrat perfect )
