What is the domain for solving the equation √(5+x)-x=3 and writing down D(g)?

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In summary, the function g(x)=√(5+x)-x has a domain of x≥-5 and when solving the equation √(5+x)-x=3, the solutions are x=-1 and x=-4.
  • #1
Jaco Viljoen
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Homework Statement


g(x)=√(5+x)-x

a) Write down D(g)

b) Solve the equation
√(5+x)-x=3

Homework Equations


√(5+x)-x=3

The Attempt at a Solution


a)
x∈ℝ: x>-5
b)[/B]
√(5+x)-x=3
√(5+x)=x+3
(5+x)=(x+3)^2
(5+x)=(x+3)(x+3)
(5+x)=x^2+6x+9
x^2+5x+4=0
(x+4)(x+1)
x=-4 or x=-1

√(5-4)--4=3
√(1)+4=3 False

√(5-1)--1=3
2+1=3 True
x=-1
 
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  • #2
you can't take sqroot of 1 -1. sqrt(x^2)=|x|
 
  • #3
Seems right. You haven't done a) though.
 
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  • #4
PWiz said:
Seems right. You haven't done a) though.
Oops, I've added my answer,

Thank you,
 
  • #5
Jaco Viljoen said:
Oops, I've added my answer,

Thank you,
That's incorrect.(Assuming that you have the condition that the output must be real.) If x were to be less than -5, then you would have to take square roots of negative numbers, so your output would no longer be real.
 
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  • #6
For a) you wrote x<-5, that is the opposite of the domain.
Your solution was x = -1. That is not in x<-5.
 
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  • #7
Utilite said:
you can't take sqroot of 1 -1. sqrt(x^2)=|x|
I don't know what you meant, but your first sentence above is incorrect. 1 - 1 = 0, and ##\sqrt{0} = 0##.
 
  • #8
PWiz said:
That's incorrect.(Assuming that you have the condition that the output must be real.) If x were to be less than -5, then you would have to take square roots of negative numbers, so your output would no longer be real.
I meant to say x>-5 so the root will not be of a negative number.
 
  • #9
Jaco Viljoen said:
I meant to say x>-5 so the root will not be of a negative number.
Yup, that's right.
 
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  • #10
Thank you,
 
  • #11
Jaco Viljoen said:

Homework Statement


g(x)=√(5+x)-x

a) Write down D(g)

b) Solve the equation
√(5+x)-x=3

Homework Equations


√(5+x)-x=3

The Attempt at a Solution


a)
x∈ℝ: x>-5[/B]

You wrote that x should be less than -5. Can you take the square root of x-5 then? So what is the correct domain of g(x)?
b)
√(5+x)-x=3
√(5+x)=x+3
(5+x)=(x+3)^2
(5+x)=(x+3)(x+3)
(5+x)=x^2+6x+9
x^2+5x+4=0
(x+4)(x+1)
x=-4 or x=-1[/QUOTE]
Correct.
Jaco Viljoen said:
√(5-4)--4=3
√(1)+4=3 False

√(5-1)--1=3
2+1=3 True
x=-1
Correct.
Is x=-1 inside the domain?
 
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  • #12
ehild said:
You wrote that x should be less than -5. Can you take the square root of x-5 then? So what is the correct domain of g(x)?
I did fix this it was a typo

ehild said:
Is x=-1 inside the domain?
Yes it is
 
  • #13
Mark44 said:
I don't know what you meant, but your first sentence above is incorrect. 1 - 1 = 0, and ##\sqrt{0} = 0##.
I
meant sqrt of 1 doesn't equal -1
 
  • #14
Jaco Viljoen said:
I meant to say x>-5 so the root will not be of a negative number.
The domain is not quite right. ##\ \sqrt{ 0 } \ ## is a real number, so -5 is in the domain.
 
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  • #15
SammyS said:
The domain is not quite right. ##\ \sqrt{ 0 } \ ## is a real number, so -5 is in the domain.
You're right. I overlooked that fact. The inequality should be weak @Jaco Viljoen
 

1. What is the domain of the function g(x)?

The domain of g(x) is all real numbers greater than or equal to -5, since the square root function cannot take negative values.

2. What is the range of the function g(x)?

The range of g(x) is all real numbers greater than or equal to 0. This is because the square root function always returns a positive value, and the subtraction of x does not affect the overall positive nature of the function.

3. What is the slope of the function g(x)?

The slope of g(x) can be found by taking the derivative of the function, which is equal to 1/2√(5+x)-1. This means that the slope is constantly changing as x increases, and the function becomes steeper as x increases.

4. Does the function g(x) have any intercepts?

Yes, g(x) has an x-intercept at -5, where the function crosses the x-axis. This can be found by setting g(x) equal to 0 and solving for x.

5. What is the behavior of the function g(x) as x approaches infinity?

As x approaches infinity, g(x) approaches a value of √5, which is the square root of the coefficient of x in the function. This can be seen by taking the limit of the function as x approaches infinity.

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