Find the Domain of Increase: y = 3x² - 6x + 4 Quadratic Function

Find the domain of increase of the function:

y=3x26x+4 y=3x^2-6x+4

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find the domains of increase of the function
00:04 We'll use the formula to find the X value at the vertex
00:09 Let's identify the trinomial coefficients
00:14 We'll substitute appropriate values according to the given data, and solve for X
00:20 This is the X value at the vertex point
00:25 The coefficient A is positive, therefore the parabola has a minimum point
00:30 From the graph, we'll deduce the domains of increase of the function
00:36 And this is the solution to the question

Step-by-step written solution

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1

Understand the problem

Find the domain of increase of the function:

y=3x26x+4 y=3x^2-6x+4

2

Step-by-step solution

The function given is y=3x26x+4 y = 3x^2 - 6x + 4 .

First, let's find the derivative of the function, which will help us determine the intervals of increase.

The derivative is given by f(x)=ddx(3x26x+4)=6x6 f'(x) = \frac{d}{dx}(3x^2 - 6x + 4) = 6x - 6 .

Next, find where the derivative is zero to locate critical points. Solve 6x6=0 6x - 6 = 0 to get:

6x=6 6x = 6
x=1 x = 1

The critical point is x=1 x = 1 . This is where the function changes from decreasing to increasing since quadratic functions have one axis of symmetry and a>0 a > 0 : indicating a parabola opening upwards.

To determine the interval of increase, analyze the sign of f(x) f'(x) :

  • For x>1 x > 1 , 6x6>0 6x - 6 > 0 which implies f(x)>0 f'(x) > 0 , so the function is increasing.
  • For x<1 x < 1 , 6x6<0 6x - 6 < 0 which implies f(x)<0 f'(x) < 0 , so the function is decreasing.

Thus, the domain of increase for the function is when x>1 x > 1 .

The correct answer is therefore x>1 x > 1 .

3

Final Answer

x>1 x > 1

Practice Quiz

Test your knowledge with interactive questions

Note that the graph of the function below does not intersect the x-axis

Moreover the parabola's vertex is A

Identify the interval where the function is increasing:

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