# To Express: The quadratic function in standard form.

### Precalculus: Mathematics for Calcu...

6th Edition
Stewart + 5 others
Publisher: Cengage Learning
ISBN: 9780840068071

### Precalculus: Mathematics for Calcu...

6th Edition
Stewart + 5 others
Publisher: Cengage Learning
ISBN: 9780840068071

#### Solutions

Chapter 3.1, Problem 16E

a.

To determine

Expert Solution

## Answer to Problem 16E

the quadratic function is expressed in standard form as  f(x)=1(x+2)2+8

### Explanation of Solution

Given: The function is f(x)=x24x+4

Calculation:

The quadratic function f(x)=x24x+4 is expressed in standard form as:

f(x)=a(xh)2+k , by completing the square. The graph of the function f is a parabola with vertex (h,k)

The parabola opens downwards if a<0 .

Solve the function:

f(x)=(x24x+4)f(x)=1(x2+4x)+4                          [factor 1 from the x terms] f(x)=1(x2+4x+4)+4(14)      [complete the square : add 4 inside parentheses, subtract (14) outside] f(x)=1(x+2)2+8                             [factor and multiply]

On comparing the above equation with standard form f(x)=a(xh)2+k ,

Therefore, the quadratic function is expressed in standard form as  f(x)=1(x+2)2+8

b.

To determine

Expert Solution

## Answer to Problem 16E

the vertex is (h,k)=(2,8) .

x-intercept is 2±6

y-intercept=f(0)=4

### Explanation of Solution

Given: The function is f(x)=x24x+4

Calculation:

The quadratic function f(x)=x24x+4 is expressed in standard form as:

f(x)=1(x+2)2+8

by completing the square. The graph of the function f is a parabola with vertex (h,k) , the vertex is (h,k)=(2,8) .

The y-intercept is given when x=0 , so y-intercept=f(0)=4

Use Quadratic formula to find the x-intercept :

x=b±b24ac2aHere; a=1, b=4, c=2x=4±(4)24(1)22(1)x=4±16+82x=4±242=2±6

The x-intercept is 2±6

c.

To determine

Expert Solution

### Explanation of Solution

Given: The function is f(x)=x24x+4

Graph:

The standard form of the function is:

f(x)=1(x+2)2+8

From the standard form it is observed that the graph is a parabola that opens downward and has vertex (2,8) . As an aid to sketching the graph, find the intercepts. The y-intercept=f(0)=4 and the x-intercept is 2±6 . The graph f is sketched in the figure below.

Use graphing calculator to graph the function: f(x)=x24x+4

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