b) x^2 - (căn bậc hai 5 + 2)x + 2 căn bậc hai 5 = 0
b) x2−(√5+2)x+2√5=0
b) x2−(√5+2)x+2√5=0
△=[−(√5+2)]2−4.1.2√5=9−4√5
√Δ=√9−4√5=√(√5−2)2=√5−2x1=√5+2+√5−22=√5;