Answer:
x² – x – 12 = (x – 4)(x + 3)
Step-by-step explanation:
Identify two numbers that add to -1 and multiply to -12, let's call them p and q.
So ax² + bx + c = (x + p)(x + q)
pq = c
p + q = b.
It is easier to find these numbers by finding factors of -12.
This can be done by splitting the number up until all the numbers are prime.
-12 → 6 × -2 or -6 × 2 → -(3 × 2 × 2)
There can only be two numbers so the only options we have are 6 and -2, -6 and 2, 3, and -4, or -3 and 4.
We can eliminate them by adding them up.
6 + -2 = 4 ≠ -1 so that can't be it.
-6 + 2 = -4 ≠ -1 so that can't be it either.
-3 + 4 = 1 ≠ -1
therefore p and q are 3 and -4 because 3 + -4 = -1.
so x² – x – 12 = (x – 4)(x + 3)
p = -4, and q = 3.
(x – 4)(x + 3) = x(x + 3) – 4(x + 3) = x² + 3x – 4x + 12 = x² – x – 12
Answer:
4 : 2: 1
Step-by-step explanation:
Answer: plan A lasts for 0.5 hour. Plan B lasts for 0.75 hour.
Step-by-step explanation:
Let x represent the duration of plan A.
Let y represent the duration of plan B.
On Friday there were 3 clients who did plan A and 2 who did Plan B.
Joe trained his Friday clients for a total of 3. It means that
3x + 2y = 3- - - - - - - - - -1
On Saturday there were 5 clients who did plan A and 6 who did plan B. Joe trained his Saturday clients for a total of 7 hours. It means that
5x + 6y = 7- - - - - - - - - 2
Multiplying equation 1 by 5 and equation 2 by 3, it becomes
15x + 10y = 15
15x + 18y = 21
Subtracting, it becomes
- 8y = - 6
y = - 6/-8
y = 0.75
Substituting y = 0.75 into equation 1, it becomes
3x + 2 × 0.75 = 3
3x + 1.5 = 3
3x = 3 - 1.5 = 1.5
x = 1.5/3
x = 0.5
The second choice is the right answer
