Answer:
3 student.
Step-by-step explanation:
From the first statement:
Let the total score be T
Let the total number of student be x
The average of the score = 72
Average = Tota score / number of student
72 = T/x
Cross multiply
T = 72x ..... (1)
Second statement:
One more student took the test and the average becomes 76 with the student having a score of 88.
Therefore,
Overall score = T + 88
Total student = x + 1
Average = 76
Average = overall score / total number of student
76 = (T + 88) /(x + 1)
Cross multiply
76(x + 1) = T + 88
Clear bracket
76x + 76 = T + 88
From equation 1
T = 72x
76x + 76 = 72x + 88
Collect like terms
76x – 72x = 88 – 76
4x = 12
Divide both side by the coefficient of x i.e 4
x = 12/4
x = 3
Therefore, the initial number of the student were 3.
A² - 225 = (a-15)(a+15)
..................................................................
Two ways:
1) guess factors(trial and error)
2) use quadratic formula.
If you use this method then a = -3, b = -6 and c = -1
x = -b +/- [sqrt(b^2 -4ac)/2a]
substituting a, b, and c into our equation we get:
x = - (-6)+/- [sqrt ((-6)^2) - 4(-3)(-1))/2 (-3)]
x = + 6 +/- [sqrt (36 -4 (3)/-6)] if I didnt make a mistake in my signs
x = + 6 +/- [sqrt (36 -12)/-6)]
x = 6 +/- [sqrt (24)/-6] but sqrt 6 x sqrt of 4 = sqrt 24 hence
x = 6 +/- [ sqrt 6 x sqrt 4 /-6] that is:
x = 6 +/- [sqrt 6 x 2 /-6 ]
so x = 6 + [sqrt 6 x 2/-6] and x = 6 - [sqrt 6 x 2/-6]
The answer to your question is 225
By definition of the binomial coefficient,
so we have
as required.
