Algebra2 expertise needed!?

Question

1)The ideal surface area of a rubber ball shipped from the factory is 50.25 square inches. The company inspector insists that the balls shipped vary no more than 0.3 square inches of this total. To the nearest hundredth, what is the minimum value for the surface area of rubber balls shipped?
50.25
49.95
50.55
none of these
2) State the possible number of imaginary zeros of f(x) = 10x3 - 4x2 + 2x - 6
exactly 1
exactly 3
3 or 1
2 or 0
3)Which describes the number and type of roots of the equation x3 - 4x2 + 50x + 7= 0?
1 positive, 2 negative
2 positive, 1 negative
3 negative
3 positive
4) Solve for x in 12=-1/7(-42x+21)
2/5
2/3
3/2
5/2

I really appreciate all your help, but the best will get the ~~~BEST ANSWER~~~!

Answer 1

1)The ideal surface area of a rubber ball shipped from the factory is 50.25 ......

50.25in^2 - .3in^2 = 49.95 in ^2 (minimum value)

2) State the possible number of imaginary zeros of
f(x) = 10x^3 - 4x^2 + 2x - 6

2 or 0.
Sign changes from (+) to a (-) to a (+) again. 3 changes means 3 positive 'real' roots. (roots = zeroes). Count down in odd numbers and you can have 3 or 1 positive real roots.
(There are no negative roots from the f(-x) test.) So, this is my reasoning. You can only have 3 total roots. If you have 3 positive real roots, then you have 0 imaginary roots. If you have 1 positive real root, then you must have 2 imaginary roots.

3)Which describes the number and type of roots of the equation x^3 - 4x^2 + 50x + 7= 0?

2 positive, 1 negative
Because the sign changes from (-) to a (+), or (+) to a (-), twice = 2 positive. The f(-x) test shows
f(-x) = (-x)^3 - 4(-x)^2 + 50(-x) + 7
f(-x) = -x^3 - 4x^2 - 50x + 7... only one sign change from (-) to a (+). So that's 1 negative.
[Descartes rule helps find 'real' roots].

4) Solve for x in 12=-1/7(-42x+21)
12=-1/7(-42x+21) ----------->Distribute the -1/7 first.
12 = 6x - 3
12 + 3 = 6x ----------------> Move the 3 to the other side by adding it.
15 = 6x ---------------->Divide by 6 to get x alone.
15/6 = x -----------------> Reduce by (3/3).
5/2 = x

Answer 2

1. is 49.95
2. it's 3 or 1 assuming that imaginary zeros is a mistake and its actually imaginary roots. Use descartes rule for finding roots
because it has 3 sign changes that means 3 positive, 0 negative, 0 imaginary, this could also be 1 positive 0 negative and 2 imaginary. As you can see there can be no negatives because if you input a -x you get no sign changes.
3. = 2 positive 1 negative using descartes rule again
4. = 5/2 because
12=-1/7(-42x+21) distribute the -1/7 and you get
12= 6x- 3
6x=15
15/6 =5/2

Answer 3

1. 49.95

2. "imaginary zeroes"? Not sure what that means.

3. One negative, two positive.

4. Ambiguous.