Step-by-step explanation:
let's look at the full numbers under the square roots when bringing the external factors back in :
sqrt(9×9×2) - sqrt(3×3×7) + sqrt(8) - sqrt(28)
and let's present these numbers as the product of their basic prime factors
sqrt(3×3×3×3×2) - sqrt(3×3×7) + sqrt(2×2×2) - sqrt(2×2×7)
now we see that we have 2 pairs of square roots : 1 pair ends with a factor of 2, and one pair with a factor of 7.
let's combine these
sqrt (3×3×3×3×2) + sqrt(2×2×2) - sqrt(3×3×7) - sqrt (2×2×7)
and now we move the factors of 2 and 7 back out in front (of course, we need to apply the square root on these factors) :
9×sqrt(2) + 2×sqrt(2) - 3×sqrt(7) - 2×sqrt(7) =
= (9+2)×sqrt(2) - (3+2)×sqrt(7) = 11×sqrt(2) - 5×sqrt(7)
and that is the first answer option.
To find the total probability, we first need to solve for the probability of the individual events.
Event 1:
P(consonant)=7/11
We know this to be true because out of the 11 total possibilities for the event, 7 of them are consonants.
R E P L A C E M E N T
Event 2
P(e)=3/10
We know this to be true because out of the 10 total possibilities for the event (since we didn't replace the first card we withdrew), 3 of them are the letter 'e'.
R E P L A C E M E N T (-1 to account for the first card we withdrew)
The possibility of both events...
P(consonant then 'e')=7/11*3/10=21/110
Answer: P=21/110
