6. a) introducem sub radical pt a putea compara nr mai usor.
x = 2√7 = √(2²*7) = √28
y = √(3²*3) = √27
=> x>y
b) rationalizam si obtinem
x = (2√5)/10 si y = (3√2)/6
Aducem fractiile la numitorul comun 30 => x=6√5/30 si y = 15√2/30
Cum ambele fractii au acelasi numitor, comaparam numuaratorii. Ii introducem sub radical => x= √180 si y= √450 => x<y
7. a) -12*15+6√15*5-4√15*3 = -40 + 6√75 - 4√45 = -30 + 30√3 - 12√5
b) (3√3 - 2√3 + 3):√3 = (√3+3):√3 = 1+ 3/√3 = 1 + 3√3/3 = 1+ √3
c) -√8 + 4*√2^(-3) + √2^5 =
-2√2 + 4*√(1/8) + 4√2 = -2√2 + 4* 1/√8 + 4√2 =
-2√2 + 4* 1/(2√2) + 4√2 =
-2√2 + √2 + 4√2 = 3√2
d) 14√5 - 7√5 -6√2 + 5√2 - 5√5 +9√2 = 2√5 + 8√2
e) 8 + 4√10 + 5 + 8 -4√10 + 55 = 26
