I need help I have tried but don't understand how to do this can someone help. the polynomial
y=-0.78x^4+3x^3+24.9

Question

I need help I have tried but don't understand how to do this can someone help. the polynomial
y=-0.78x^4+3x^3+24.9

moonlitfate · Answer

What are you supposed to be doing with it, exactly? :O

anonymous · Answer

that's all it gave me to solve :the polynomial
y=-0.78x^4+3x^3+24.9

moonlitfate · Answer

Solving for x, then? :)

anonymous · Answer

no i'm solving for y

moonlitfate · Answer

Are you sure that the problem is written correctly?

anonymous · Answer

yeah its y= -0.78x to the forth + 3x to the third power + 24.9

anonymous · Answer

The polynomial

y = -0.78 x^4 + 3 x^3 + 24.9

describes the billions of flu virus particles in a person’s body x days after being infected. Find the number of virus particles, in billions, after 2 days.

There are  billion virus particles in a person’s body 2 days after being infected.

moonlitfate · Answer

Ahh, okay!  That makes more sense then.

moonlitfate · Answer

Basically x = the number of days after a person is infected with the flu; x can be any positive number. You can't have negative virus particles.

moonlitfate · Answer

So, how do you figure out how many particles are in a person's body after two days?  Since the problem tells you that x is the number of days.  You going to plug in 2 for every x in that polynomial.  Understand so far? :)

anonymous · Answer

so it would be -0.78*2^4+3*x^3+24.9

anonymous · Answer

or it would be -0.782^4+32^3+24.9

moonlitfate · Answer

$$y = -0.78x^4+3x^3+24.9$$
Solve the polynomial when x = 2
$$y = -0.78(2)^4+3(2)^3+24.9$$

moonlitfate · Answer

So, when x = 2; what does y equal? :)

moonlitfate · Answer

@noemi -- Hopefully you understand.

anonymous · Answer

im trying to solve it

anonymous · Answer

so this is what i did $$y= -1.56^4+6^3+24.9$$

moonlitfate · Answer

Okay, you seem to have gotten the multiplication and exponents order confused.

moonlitfate · Answer

Order of operations: Exponents always go first. :)

moonlitfate · Answer

So, it would be:

$$y = -0.78(16)+3(8)+24.9$$

See, what I did there?

anonymous · Answer

so it would be 36.42

moonlitfate · Answer

Yes. :)  So, to answer your original problem: after 2 days of being infected with the flu, how many billions of flu virus particles are in a person's body?

anonymous · Answer

y=36.42 billion virus

moonlitfate · Answer

Yep. :) Any more questions about anything?

anonymous · Answer

i think im good for now thanks you are awesome

moonlitfate · Answer

Aww, thank you!  And you're very welcome.