Find Intersection of -sqrt(x) & x-6 Functions

  • Thread starter zeion
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In summary, to find the point at which two functions intersect, you must set the functions equal to each other, manipulate the equation to get it in the form of x = some expression, and then solve for x using algebraic methods. Make sure to check each solution in the original equation to avoid extraneous solutions. Alternatively, you can use a substitution method to solve the equation.
  • #1
zeion
466
1

Homework Statement



I need to find the point at which these functions intersect:
y = -sqrt(x)
y = x - 6


Homework Equations





The Attempt at a Solution



I set them to equate:
-sqrt(x) = x - 6
-sqrt(x) - x + 6 = 0

Now how do I find the root?
 
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  • #2
equate them tgt , [tex]\sqrt{x}=6-x[/tex] .
Now square both sides , x=36+x²-12x ... continue from here.
 
  • #3
Do I move them all to one side and get x^2 -13x + 36 = 0?
 
  • #4
Yes. Now factor.

Be sure to check each solution in the original equation, though. When you square both sides of an equation, extraneous solutions are sometimes introduced, values that are not solutions of your original equation.
 
  • #5
Alternatively, you can say u=sqrt(x) and rewrite the equation as -u-u^2+6=0
 
  • #6
Okay nice.
So I can't use x = 9 because -sqrt(9) not= 9-6, correct?
 
  • #7
Ah okay, that u substitution seems easier:
Let u = sqrt(x), then
u^2 + u - 6 = 0
(u+3)(u-2) = 0
u = -3, u = 2
sqrt(x) = -3, sqrt(x) = 2
x = 9, x = 4
 
  • #8
Thanks guys!
 
  • #9
zeion said:
Ah okay, that u substitution seems easier:
Let u = sqrt(x), then
u^2 + u - 6 = 0
(u+3)(u-2) = 0
u = -3, u = 2
sqrt(x) = -3, sqrt(x) = 2
x = 9, x = 4
But x = 9 is not a solution of sqrt(x)= 6 -x, which is what you started with. x = 9 is an extraneous solution that I warned you of.
 

Related to Find Intersection of -sqrt(x) & x-6 Functions

1. What is the "Find Intersection of -sqrt(x) & x-6 Functions" problem?

The "Find Intersection of -sqrt(x) & x-6 Functions" problem asks for the values of x where the two functions, f(x) = -sqrt(x) and g(x) = x-6, intersect. In other words, we need to find the value(s) of x that make both functions equal to each other.

2. How do you solve the "Find Intersection of -sqrt(x) & x-6 Functions" problem?

To solve this problem, we need to set the two functions equal to each other and then solve for x. This can be done using algebraic methods, such as isolating x on one side of the equation and simplifying. Once we have the value(s) of x, we can plug them back into the original functions to find the corresponding y-values.

3. Are there any restrictions or limitations when solving the "Find Intersection of -sqrt(x) & x-6 Functions" problem?

Yes, there are restrictions when solving this problem. Since the function f(x) = -sqrt(x) is undefined for negative values of x, we can only find intersections for values of x that make both functions defined. In this case, x must be greater than or equal to 0.

4. Is there a graphical method for finding the solutions to the "Find Intersection of -sqrt(x) & x-6 Functions" problem?

Yes, we can use a graphing calculator or software to graph the two functions and visually find the points where they intersect. This can give us an approximate solution, but it is important to note that it may not be exact due to the limitations of graphing technology.

5. Can the "Find Intersection of -sqrt(x) & x-6 Functions" problem have more than one solution?

Yes, it is possible for this problem to have more than one solution. Since the two functions are not parallel, they can intersect at multiple points. It is important to check all potential solutions to ensure that they are valid and satisfy the restrictions mentioned in question 3.

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