# math

How do I know that x^2-7=y is a function? thanks

you know its a function because its a parabola (x^2)

parabolas are functions because there is only one x value per y value.

So I know it is a function because it has (x^2)? Is that the rule? If it has x^2, it's a function and if it doesn't, it's not a function?

no, its a function if there is only one x value per y value. for example, a circle is not a function, because there are two y values for one x value.

if something is an x^2, you know its a parabola. and a parabola is one of many examples of a function.

How do you tell if there is only one x per y by just looking at an equation such as (x-4)/3=y?

generally, if the equation can be solved for y as a single expression in such a way that the other side contains only x's and constants, then it is a function.

if, when graphed, you visualize a vertical line scanning from left to right, if the vertical line crosses or touches the graph in more than one place for any value of x then it is NOT a function (the verical line test)

what is a constant?

so are most equations usually functions unless y=a squareroot, such as y=sqrtx+6

a constant is a numerical value without a variabe
eg. in y = 7x+5, the 5 is a constant.

even equations like y=SQR(x^2-9) are considered functions, since by the definition the SQR yields only a positive result.

However when you have somthing like
x^2+y^2=100, which is a circle, then when you solve for y you would get
y^=100-x^2 and then
+y=SQR(100-x^2) or -y=SQR(100-x^2)
which we normally write as
y=+/-SQR(100-x^2)
notice that y is written as two different equations, thus NO function

yeah, that's what i meant, when the answer is a squareroot

y=sqrt(100-x^2) would be a function since y was written as a single unique expression and for each x of the domain you got one and only one y value.

-

1. 👍 0
2. 👎 0
3. 👁 85

## Similar Questions

1. ### pre calc

The Identity Function The Squaring Function The Cubing Function The Reciprocal Function The Square Root Function The Exponential Functional Lo The Natural Logarithum Function The Sine Function The Cosine Function The Absolute

asked by kim on December 18, 2009
2. ### Algebra 1

Which of the following statements is true about the function y = 5⋅x4 ? It is an even function It is an odd function It is an exponential function It is an inverse function

asked by Jamie Ciacico on August 14, 2015
3. ### College Algebra

1.Give a quadratic function q(x) with a vertex of (-1, 2). 2. Give a function h(x) which does not have an inverse function. 3. Give a polynomial function g(x) with zeros 1,2,3 4. Give an exponential function s(x) passing through

asked by Chris on July 25, 2014
4. ### algebra

Give am example of a function f.N N with the property that there exists a function g. N N such that the composition got is the identity function on N but for no function h. N N does it hold that fog is the identity function on

asked by geeta on February 27, 2014
5. ### Math

Create a function that closely gives the graph given in the link. The function may be a piecewise function but it does not necessarily have to be a piecewise function. a. Give a brief narrative explaining what you did to create

asked by Fatih on February 27, 2012
6. ### Calculus HELP ASAP

Listed below are four types of functions. Which does not possess a derivative of the same type? a) exponential function b) logarithmic function c) sinusoidal function d) linear function e) NO RESPONSE

asked by Anonymous on January 23, 2019
7. ### Math

How would you rewrite the equation y = 3x+1 as a function of x. Hmmm. It is written now as a function of x. Do you mean like this, where x is a function of y? x= 1/3 y -1 ? Could this be a trick question? I thought It was already

asked by Erin on May 6, 2007
8. ### Math

flickr.(dotcom)/photos/77304025@N07/6782789880/ Create a function that closely gives the graph given below. The function may be a piecewise function but it does not necessarily have to be a piecewise function. a. Give a brief

asked by Fatih on February 27, 2012
9. ### Calculus

flickr.(dotcom)/photos/77304025@N07/6782789880/ Create a function that closely gives the graph given below. The function may be a piecewise function but it does not necessarily have to be a piecewise function. a. Give a brief

asked by Fatih on February 27, 2012
10. ### Math

1. Function Q and function R are both linear functions. Function Q has an x-intercept at (4,0), and the slope is 1/4. Function R is represented by the table. x y -4 14 3 0 5 -4 Which statement is true? A. Function Q has a larger

asked by BTS on March 8, 2019
11. ### Math

0.08x^3 + 0.6x+2.8 absolute-value function Rational function Another polynomial function Quadratic function

asked by Anonymous on November 23, 2013

More Similar Questions