f(x) = -x^2 + 2 ordered pairs

Question

(-1, 1)

B

(-1, -1)

C

(-2, -2)

D

(2, -2)

E

(-2, 2)

these are the options but i forgot how to find the answer to it i know you use the procces of elimination and have to have it in slope intercept form but im lost past that...

Answer 1

if the ordered pair is on the graph, then it will be like this: (x, f(x))

what you want to do is take the first number, put it into the function, and see if the answer is the 2nd number

lets try it:

A and B: we need to see what (-1, f(-1)) is.

f(-1) = -(-1)^2 + 2 = -1 + 2 = 1

so (-1, 1) is in the graph. A is an answer and B isnt.

C and E: we need to see what (-2, f(-2)) is

f(-2) = -(-2)^2 + 2 = -4 + 2 = -2

so (-2, -2) is in the graph. C is an answer and E isnt.

D: we need to see what (2, f(-2)) is

here's a trick: a function y = ax^2 + b is even. so f(x) = f(-x). you can calculate it directly or use that.

f(2) = f(-2) = -2

so (2, -2) is in the graph. D is an answer.

Putting it all together, A, C, and D are in the graph.

Answer 2

Hey Bryce.

You can solve this by plugging the first value of each ordered pair in place of X on the right side of the equation, then see if the answer you get is the same the the Y value of the same ordered pair.

f(x)=-x^2+2

Remember that f(x) is the output of the function, meaning it's the same thing as Y.

f(-1)=-(-1)^2+2

=-(1)+2

=-1+2

= 1

when X = -1, Y = 1. So the ordered pair that works is a. (-1,1)

Hope this helps.

michael.russell.10