The position of the particle as function of time is given as

The velocity as function of time is

A graph of f(t) versus t and of v(t) versus t is shown below.
The velocity increases in the intervals t = (2, 6) and t = (10, 14) and with a periodicity of 8.
In the range t = [0, 16], the velocity increases in the interval t = (2,6)∪(10, 14).
Answer: (2,6)∪(10,14)
We can replace the inequality with qual sign:
2x - y = 4
x + y = -1
We can combine both question
3x = 3
x = 1
Since we know x = 1, we can solve for y by plug in in either equation:
x + y = -1
1 + y =-1
y = -2
or
2x - y = 4
2(1) - y = 4
-y = 2
y = -2
So the solution of this system of equation is the coordinate (1, -2)
Length of DA: 90°
They are placed on a obtuse angle, which is 180° and DA are also placed on a right angle, so that means 180°-90°=90°
Length of AB: 180°
Their placed on a obtuse angle, therefore it will just be 180°
ADF=BDE because, both of them are right angles. This means their degrees will equal (90°=90°).
Hopefully this helps, sorry if I turn out to be wrong!