Let g be the number of grandchildren, and d be the number of dogs. They both have only one head, so the number of heads is
Grandchildren have 2 legs, while dogs have 4. So, the total number of legs is
From the first equation (the one for the heads) we can derive
Substitute this into the second to get
So, there are 9 dogs and (from the first equation
a)
b) See interpretation below
Step-by-step explanation:
a)
The motion of both balls is a free-fall motion: it means that the ball is acted upon the force of gravity only.
Therefore, this means that the motion of the ball is a uniformly accelerated motion, with constant acceleration equal to the acceleration of gravity:
in the downward direction.
For the ball dropped from the initial height of , the height at time t is given by
(1)
The ball which is thrown upward from the ground instead is fired with an initial vertical velocity , and its starting height is zero, so its position at time t is given by
(2)
Therefore, the polynomial that represents the distance between the two balls is:
b)
Now we interpret this polynomial, which is:
which represents the distance between the two balls at time t.
The interpretation of the two terms is the following:
- The constant term, , is the initial distance between the two balls, at time t=0 (in fact, the first ball is still at the top of the building, while the second ball is on the ground). For this problem,
- The coefficient of the linear term, , is the initial velocity of the second ball; this terms tells us that the distance between the two balls decreases every second by
feet.