Answer:

Step-by-step explanation:
From the question we are told that:
Function given

Co-ordinates
(x,y)=[1, 4]
Generally the second differentiation of function is mathematically given by

Therefore critical point

Generally the substitutions of co-ordinate into function is mathematically given by
For 1

For 4

For critical point 3

Therefore the maximum value of f(x) = –x2 + 6x over the interval [1, 4] is given by

You would distribute then combine like terms to get your answer.
They must sell, 30 cups of lemonade. How I got my answer.
Since it cost $1.20 to start, and a cup of lemonade cost $0.6 to make and there selling them at $0.10 each. So we know they are making a $0.4 profit off of each cup of lemonade. We now have to multiply 4×30=120.
I hope this helps!
Pi/4 radians
You're looking for the angle that has a secant of sqrt(2). And since the secant is simply the reciprocal of the cosine, let's take a look at that.
sqrt(2) = 1/x
x*sqrt(2) = 1
x = 1/sqrt(2)
Let's multiply both numerator and denominator by sqrt(2), so
x = sqrt(2)/2
And the value sqrt(2)/2 should be immediately obvious to you as a trig identity. Namely, that's the cosine of a 45 degree angle. Now for the issue of how to actually give you your answer. There's no need for decimals to express 45 degrees, so that caveat in the question doesn't make any sense unless you're measuring angles in radians. So let's convert 45 degrees to radians. A full circle has 360 degrees, or 2*pi radians. So:
45 * (2*pi)/360 = 90*pi/360 = pi/4
So your answer is pi/4 radians.
1/2r -3= 3 (4-3/2r) is to be solved for r.
I'll begin by making the assumptions that by 1/2r you actually meant (1/2)r and that by 3/2r you actually meant (3/2)r. When in doubt, please use parentheses to make your meaning clear.
Thus, 1/2r -3= 3 (4-3/2r) becomes (1/2)r -3= 3 (4-(3/2)r ) .
Simplify this by multiplying all 3 terms by 2. Doing this will eliminate the fractions:
r -6 = 3 (4*2-(3)r ) or r - 6 = 24 - 9r
Now expand the right side, using the distributive property of
r - 3 = 24 - 9r
Regrouping so as to combine like terms:
10r = 30
Solving for r: r = 30/10 = 3
The value of r that satisfies this equation is 3