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AfilCa [17]
3 years ago
7

A video rental store charges $4 per day to rent a movie and $3 per day to rent a video game. During one summer, Tony paid a tota

l of $140 to rent movies and video games from this store. If he rented twice as many video games as movies, how much did he spend on movie rentals during the summer?
Mathematics
1 answer:
Colt1911 [192]3 years ago
4 0
Let's use the variables m and v for this:
4m + 3v = 140
v = 2m
Insert this variable:
4m + 3(2m) = 140
4m + 6m = 140
10m = 140
m = 14
One movie costs 4 dollars:
14*4 = 56
He spent $56 on movies
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3. The curve C with equation y=f(x) is such that, dy/dx = 3x^2 + 4x +k
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a. Given that y = f(x) and f(0) = -2, by the fundamental theorem of calculus we have

\displaystyle \frac{dy}{dx} = 3x^2 + 4x + k \implies y = f(0) + \int_0^x (3t^2+4t+k) \, dt

Evaluate the integral to solve for y :

\displaystyle y = -2 + \int_0^x (3t^2+4t+k) \, dt

\displaystyle y = -2 + (t^3+2t^2+kt)\bigg|_0^x

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Use the other known value, f(2) = 18, to solve for k :

18 = 2^3 + 2\times2^2+2k - 2 \implies \boxed{k = 2}

Then the curve C has equation

\boxed{y = x^3 + 2x^2 + 2x - 2}

b. Any tangent to the curve C at a point (a, f(a)) has slope equal to the derivative of y at that point:

\dfrac{dy}{dx}\bigg|_{x=a} = 3a^2 + 4a + 2

The slope of the given tangent line y=x-2 is 1. Solve for a :

3a^2 + 4a + 2 = 1 \implies 3a^2 + 4a + 1 = (3a+1)(a+1)=0 \implies a = -\dfrac13 \text{ or }a = -1

so we know there exists a tangent to C with slope 1. When x = -1/3, we have y = f(-1/3) = -67/27; when x = -1, we have y = f(-1) = -3. This means the tangent line must meet C at either (-1/3, -67/27) or (-1, -3).

Decide which of these points is correct:

x - 2 = x^3 + 2x^2 + 2x - 2 \implies x^3 + 2x^2 + x = x(x+1)^2=0 \implies x=0 \text{ or } x = -1

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2 years ago
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Which statement is true about the result of a rigid transformation?
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I think the answer is a
6 0
3 years ago
Activity
FrozenT [24]

Answer:

Step-by-step explanation:

For the first 30 hours, Andrew will earn 4(30) = $120.  For each additional hour beyond 30 that Andrew works, he will earn 5(h - 30).  Therefore, the function that gives Andrew's total wages when he works more than 30 hours is:

 

w = 120 + 5(h - 30).  

 

So, if he works 35 hours, he will earn:

 

120 + 5(35 - 30) = 120 + 5(5) = 120 + 25 = $145.

 

If he works 42 hours, he will earn:

 

120 + 5(42 - 30) = 120 + 5(12) = 120 + 60 = $180.

 

I hope this helps!

7 0
3 years ago
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