# Maths proportion question help

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#1
Hey guys i need help, on question 16 of this booklet. I know graph D is the first statement, but i don't know the rest. Thanks.

http://www.esherhigh.surrey.sch.uk/u...0_Paper_1H.pdf
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5 years ago
#2
Let's start off with the easier ones. If you don't know already, a quadratic is a U-shaped graph. So if we create a formula for y being proportional to the square of x, we get y = kx^2, where k any constant. We see that x has a power of ^2, which is the greatest power, so it must be a quadratic. Now, this must match up with graph B.

For inversely proportional, we know the formula will look something like this. y= k/x, where k is a constant. Let's say for example that k is equal to 1, and x is equal to 0.01. So now we have y=1/0.01, which means y= 100. We do this when x = 0.02, y will equal 50. So when x is smallest, y will be greatest (and vice versa). If we plot a couple of points similar to the ones I just mentioned, you'll get a graph that looks like graph A.
We only have 1 graph left, which means graph C must be inversely proportional to the square of x.
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