Please help me with this question, and show working out.
1 answer:
<h3>Answer: 2072.4 square cm</h3>
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Explanation:
If you used scissors to cut a vertical slice down the lampshade, then it can be unrolled to form a rectangle.
The horizontal portion of this rectangle is the distance around the circle, which is the perimeter of the circle, or the circumference. That's C = 2pi*r. Check out the diagram below to see what I mean.
The diagram shows that the diameter is 20 cm, so the radius is half that at 20/2 = 10 cm.
The circumference is C = 2*pi*r = 2*pi*10 = 20pi cm exactly
The height of the rectangle is the height of the cylinder, which is h = 30 as shown in the diagram.
The area of the rectangle is length*height = (20pi)*(30) = 600pi square cm exactly.
If we were to use something like pi = 3.14, then its approximate area is 600*pi = 600*3.14 = 1884 square cm
Let's bump this up by 10%. To do so, we'll multiply by 1.10
1.10*1884 = 2072.4
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Answer:
Step-by-step explanation:
In order to determine the information you're being asked for, you need to complete the square on that quadratic. The first step is to move the constant over to the other side of the equals sign:
Here would be the step where, if the leading coefficient isn't a 1, you'd factor it out. But ours is a 1, so we're good there. Now take half the linear term (the term with the single x on it), square it, and add it to both sides. Our linear term is a -2. Half of -2 is -1, and -1 squared is +1. We add +1 to both sides giving us this:
Now we'll clean it up a bit. The right side becomes a 4, and the left side is written as its perfect square binomial, which is the whole reason we did this. That binomial is
(set equal to the 4 here). Now we'll move the 4 back over and set the whole thing back equal to y:
From this it's apparent what the vertex is: (1, -4),
the axis of symmetry is x = 1, and
the y-intercept is found by setting the x's equal to 0 in the original equation and solving for y. So the y-intercept is (0, -3).
Your choice for the correct answer is the very last one there.