Jika x = 6 - 2√5 dan y = 6 + 2√5 tentukan nilai dari: a. 2x² + 2y b. x² + y² c. 3x√5 + 3y √3 d. 2xy

x = 6 - 2√5
y = 6 + 2√5
a. 2x^2 + 2y
= 2(6-2√5)(6-2√5) + 2(6+2√5)
= 2(36 -12√5 -12√5 +4•5) + 12 +4√5
= 2(36 -24√5 +20) +12 +4√5
= 2(56 -24√5) +12 +4√5
= 112 -48√5 +12 +4√5
= 124 -44√5
b. x^2 + y^2
= (6-2√5)^2 +(6+2√5)^2
= (36-2•12√5+4•5) +(36+2•12√5+4•5)
= (36-24√5+20) +(36+24√5+20)
= (56-24√5) +(56+24√5)
= 112
c. 3x√5 +3y√3
= 3(6-2√5)√5 +3(6+2√5)√3
= 18√5 -6•5 + 18√3 +6√15
= 18√5 +18√3 +6√15 -30
d. 2xy = 2(6-2√5)(6+2√5)
= 2(36 +12√5 -12√5 -4•5)
= 2(36 -20)
= 2(16)
= 32