We have
x² + 24x = 17 (1)
Note that
(x + 12)² = x² + 24x + 144
By adding 144 to the left side of equation (1), it becomes a perfect square.
Therefore
x² + 24x = (x+12)² - 144 (2)
Substitute (2) into (1).
(x + 12)² - 144 = 17
(x + 12)² = 17 +144
(x + 12)² = 161
Answer:
We added 144 to the left side of equation (1) in order to make it a perfect square.
The probability that the number picked is less than 84 p(A) is:
number of possible events with picked number less than 84/ total number of possible events = 4/7
The complement event of A is that event A does not occur. If the picked number is not less than 84 ( this means is greater than 84 or is 84). The probability of the complement event is:1- p(A)=3/7
Solution: B
