Answer:
1120 combinations of four teachers include exactly one of either Mrs. Vera or Mr. Jan.
Step-by-step explanation:
The order in which the teachers are chosen is not important, which means that the combinations formula is used to solve this question.
Combinations formula:
is the number of different combinations of x objects from a set of n elements, given by the following formula.
In this question:
1 from a set of 2(Either Mrs. Vera or Mr. Jan).
3 from a set of 18 - 2 = 16. So

1120 combinations of four teachers include exactly one of either Mrs. Vera or Mr. Jan.
Step-by-step explanation:
x² + 4x - 9
= (x + 2)² - 13
a = 2, b = -13.
Answer:
i cant see it can you explain it
Step-by-step explanation:
Answer:

Step-by-step explanation:
we know that
A relationship between two variables, x, and y, represent a direct variation if it can be expressed in the form
or 
In this problem we have
y=18 when x=2
Find the value of the constant of proportionality k
----> 
therefore
The equation is equal to

Answer:
Minimum 66 feet of molding that he needs.
Step-by-step explanation:
Given that a square ceiling has a diagonal of 23 ft.
If the sides of the square ceiling are 'a' feet, then applying Pythagoras Theorem we can write, a² + a² = 23²
⇒ 2a² = 23²
⇒ a = 16.2634 feet (Approximate)
Now, the perimeter of the square ceiling will be 4a = 65.05 feet.
If the cost of molding along the perimeter of the ceiling is in per foot, then a minimum of 66 feet of molding that he needs. (Answer)