If x = √(23 + 6√10) − √(23 − 6√10), then the value of x lies between:

Explanation

23 ± 6√10 = (√18 ± √5)², so x = (√18 + √5) − (√18 − √5) = 2√5 ≈ 4.47, which lies between 4 and 4.5.