#1**+1 **

1. We could do some math here.....but.....using logic is better

Note that if we put 0 into these functions....the result wll just be the last term

So....since (0,2) is on the graph....the last term will be + 2

There are only two answers that are possible

Now...think about this......

Since (-2, 18) and (0,2) are on the graph...it must "higher" on y at x = -2 than it is at x = 0

And it rises back to 42 at x = 4

So...this parabola must turn upward [ graph these points, NSS, to convince yourself of this ]

So remember that a parabola that turns upward always has a positive first term

So....by elimination....the third answer is correct...the first term is positive and the last term is + 2

CPhill
Nov 1, 2017

#2

#4**+1 **

Not B

Note that when we put 0 into the function we get -6 as the last term..... and (0,-6) is on the graph

And like the first problem.....the y values as we move from left to right decrease and increase again......so....the parabola turns upward....this means that the lead term is positive...so the correct answer is one of the last two

Put -2 into the third function

5(-2)^2 + 4(-2) -6 = 20 - 8 - 6 = 6

So....(-2, 6) is on this graph.....but we have that (-2,0) is on the graph

So...the last function must be correct

Note

4(-2)^2 + 5(-2) - 6 = 16 - 10 - 6 = 0

So.... (-2, 0) is on this graph....si....it must be the correct choice

CPhill
Nov 1, 2017