3.
√250 = √(25 * 10) = √(5^2 * 10) = √(5^2) * √10
… = 5 √10
=> a = 5
4.
√(-300) = √(-1 * 3 * 100) = √(-1 * 3 * 10^2) = √(-1) * √3 * √(10^2) = i * √3 * 10
… = 10i √3
=> -a = 10 and b = 3 => a = -10 and b = 3
=> a - b = -10 - 3 = -13
