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

Question

Find the domain of increase of the function:

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

Video Solution

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 .

Answer

x > 1