12 x 16 = 192. So, the room is 192 square feet.
Set the whole expression = to 0 and solve for x.
3x^(5/3) - 4x^(7/3) = 0. Factor out x^(5/3): x^(5/3) [3 - 4x^(2/3)] = 0
Then either x^(5/3) = 0, or 3 - 4x^(2/3) = 0.
In the latter case, 4x^(2/3) = 3.
To solve this: mult. both sides by x^(-2/3). Then we have
4x^(2/3)x^(-2/3) = 3x^(-2/3), or 4 = 3x^(-2/3). It'd be easier to work with this if we rewrote it as
4 3
--- = --------------------
1 x^(+2/3)
Then
4
--- = x^(-2/3). Then, x^(2/3) = (3/4), and x = (3/4)^(3/2). According to my 3 calculator, that comes out to x = 0.65 (approx.)
Check this result! subst. 0.65 for x in the given equation. Is the equation then true?
My method here was a bit roundabout, and longer than it should have been. Can you think of a more elegant (and shorter) solution?
1st question
make line plot similar to the second. above 1/6 put 6 x's; above 1/3 put 3 x's; above 1/2 put 6 x's.
average: 1/3
Answer:
We want a polynomial of smallest degree with rational coefficients with zeros in 
, 
and -3. The last root gives us the factor (x+3). Hence, our polynomial is
where 
is a polynomial with rational coefficients and roots and . The root gives us a factor 
, but in order to obtain rational coefficients we must consider the factor 
.
An analogue idea works with . For convenience write 
. This gives the factor 
. Hence,
Notice that 
. So, in order to satisfy the last condition we divide by 3 the whole polynomial, without altering its roots. Finally, the wanted polynomial is
Step-by-step explanation:
We must have present that any polynomial it's determined by its roots up to a constant factor. But here we have irrational ones, in order to eliminate the irrational coefficients that a factor of the type 
will introduce in the expression, we need to multiply by its conjugate 
. Hence, we will obtain that have rational coefficients. Finally, the last condition is given with the intention to fix the constant factor. Usually it is enough to evaluate in the point and obtain the necessary factor.
