Question

How is this a function

y= √(x+2

the textbook says its a function but I thought when we square root a number the answers can be either a positive or a negative

Answer 1

use vertical line test

http://www.wolframalpha.com/input/?i=plot+sqrt%28x%2B2%29

Answer 2

Yea your right ! thanks =)

Answer 3

but when you plug in an x value we get 2 y values ?

Answer 4

Say we use x = 2 then then y could possibly be +2 or -2?

Answer 5

@cinar

Answer 6

no not like that..

Answer 7

but when we square root something we can either have a postiive or a negative

Answer 8

if x^2=4, then x=-+2

but here if x=2, then y=2

Answer 9

I get the first part but...

Answer 10

@nincompoop

Answer 11

@jim_thompson5910

Answer 12

cinar is absolutely correct

there are two solutions to x^2 = 4, and they are x = 2 or x = -2

but the square root function is a function because plugging in any nonnegative real number for x produces EXACTLY ONE nonnegative real number for y

Answer 13

so yes x^2 = k has two solutions x = plus/minus sqrt(k)

but the square root function itself produces one output per input, and this output is either 0 or positive

if you want negative outputs, you have to force it to be negative by sticking a negative out front like this: -sqrt(k)