<span>If all your entries are integers, the determinant is also an integer.
</span>For this problem, 1 0
0 13
For this question, you should just fix 3 values and make the 4th value an unknown and solve it.
I hope my answer helped you somehow.
Answer:
It's C
Step-by-step explanation:
Your graph should be this one, with both lines solid because, the X line, or red, has to be at least -1 or higher, and the Y line, or the blue, has to be +4 or higher
Then, 15 - x is the distance ran in the second part.
The time, t1, for the first part is t1 = xmi / 8mi/h
The time, t2, for the second part is t2 = (15 - x)mi / 20mi/h
The total time is t1 + t2 = 1.125 h
Then x/8 + (15 - x) / 20 = 1.125
To solve for x, multiply both sides by 40 (this is the least common multiple)
5x + 30 - 2x = 45
3x = 15
to find x divide: 15/3=5
And 15 - x = 10 mi.
First part:
Speed: 8mi/h
Distance: 5 mi
Time: 5mi/8mi/h = 5/8 h = 37.5 minutes
Second part
Speed: 20 mi/h
Distance: 10 mi
Average speed: 15mi/1.125h =13.33 mi/h
Distance: 15mi
Time: 1.125 h = 67.5 minutes
