The graphs shown are of the form y = ax2. Which graph has the smallest value for a?

1 answer:

3 0

$y= x^{2}$ is a parabola (looks like the letter U).

The letter a represents the coefficient of $x^{2}$ and it controls two things (1) how wide or narrow the parabola is and (2) whether it is concave up (like a U) or concave down (like an up-side-down).

The absolute value of a (the number without the sign) controls how wide or narrow it is. If the absolute value is a fraction less than 1 the graph gets wider. The smaller the absolute value of the fraction the wider the graph gets.

If the absolute value of a is greater than 1 the graph gets narrower (it gets skinnier). The bigger the absolute value the narrower the graph.

So, if all the graphs look like a U (concave up) then the one with the smallest a is the one that is the widest.

The a also controls whether the graph is concave up or concave down. If a is negative

If a is negative the graph is concave down so any graph that is concave down has a smaller value of a than any graph that is concave up. However, if the graph is concave down the one with the smallest a would be the most narrow one.

So to find the one with the smallest a...
If they are all concave up (like a U) pick the widest one
and
If they are not all concave up pick the narrowest one that is concave down (looks like an upside down U)

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Given circle X with radius 10 units and chord AB with length 12 units, what is the length of segment CX, which bisects the chord

andrew-mc [135]

Consider the circle with center X, as shown in the figure.

Draw the diameter of the circle which is parallel to cherd AB, as shown in the figure.

Since the diameter and AB are parallel, then the line segment XC which bisects AB at C, will be perpendicular to AB.

SO triangle XCB is a right triangle. Thus the length of CX, by the Pythagorean theorem is

$\sqrt{ XB^{2}- CB^{2}} = \sqrt{ 10^{2}- CB^{6}}= \sqrt{100-36}= \sqrt{64}=8$ units.

Answer: 8 units