Mathematics for IGCSE & O level - Surds (Section 2 - No. 28)
Which of the following results in a rational number?
(2+√3) + (2-√3)
(√3 + 1) * (√3 - 1)
√2 + √8
(√5)^3
Giải thích
(2 + √3) + (2 - √3) = 4; (√3+1)(√3-1) = 2; √2 + √8 = 3√2 (irrational); (√5)^3 = 5√5 (irrational)