Since 
and 
are roots of 
, we can factorize the quadratic in terms of the roots as
Expanding the right side gives
so that
A polynomial with roots 
and 
would be
and expanding this gives
Now,
and
So we can write the second quadratic in terms of 
as
and to make things look cleaner, scale the whole expression by 
to get
Order is important in ratios so in this one, it says the ration from GIRLS to BOYS.
We know there are 12 girls and 9 boys so the ratio is B. 12:9
So we are given the mean and the s.d.. The mean is 100 and the sd is 15 and we are trying the select a random person who has an I.Q. of over 126. So our first step is to use our z-score equation:
z = x - mean/s.d.
where x is our I.Q. we are looking for
So we plug in our numbers and we get:
126-100/15 = 1.73333
Next we look at our z-score table for our P-value and I got 0.9582
Since we are looking for a person who has an I.Q. higher than 126, we do 1 - P. So we get
1 - 0.9582 = 0.0418
Since they are asking for the probability, we multiply our P-value by 100, and we get
0.0418 * 100 = 4.18%
And our answer is
4.18% that a randomly selected person has an I.Q. above 126
Hopes this helps!
1:50 mean u would multiply 30 by 50 which equals 1500
