The interval (− ∞ , 2) includes all negative numbers AND all positive numbers less than 2.
We have to see if 1.98 belongs to the interval
Since 1.98 < 2, then yes it belongs to the interval
Now, we have to find 2 numbers greater than 1.98 that also belong to the interval.
Now we have to increase the decimal points of 1.98 such that the resulting number is less than 2. One such number can be 1.98+0.01 = 1.99. The other number can be 1.98+0.001=1.981. Hence, there can be infinite such numbers
Next, we have to check if it is possible to find the greatest number that belongs to that interval. No it is not, because we can put infinite number of digits after the decimal point in 1.99 such that the resulting number is still less than 2.
Similarly, it is not possible to find the smallest number on the interval, as we can put as many digits in a negative number, to make it lower than the previous number.