Question

Sketch the graph of each of the following quadratic functions. (a) f(x) = x² - 4x - 5 for -2 ≤ x ≤ 6.

Answer 1

To sketch the graph we have to solve the function with each value of x to get the coordinates.

f(x) = x² − 4x − 5

−2 ≤ x ≤ 6

This inequality represents the domain for x. Therefore x is greater than equal to -2 but less than equal to 6.

The range of x is as follows:

x = -2, -1, 0, 1, 2, 3, 4, 5, 6

We already have the values for x therefore, we must substitute the values of x into the function f(x) = x² − 4x − 5 to find the y values.

Solutions:

For x = -2

f(x) = x² − 4x − 5

= -2² − 4(-2) - 5

= 4 + 8 - 5

= 7

Point = (-2,7)

For x = -1

f(x) = x² − 4x − 5

= -1² - 4(-1) - 5

= 1 + 4 - 5

= 0

Point = (-1,0)

For x = 0

f(x) = x² − 4x − 5

= 0² - 4(0) - 5

= 0 - 0 - 5

= -5

Point = (0,-5)

For x = 1

f(x) = x² − 4x − 5

= 1² - 4(1) - 5

= 1 - 4 - 5

= -8

Point = (1,-8)

For x = 2

f(x) = x² − 4x − 5

= 2² - 4(2) - 5

= 4 - 8 - 5

= -9

Point = (2,-9)

For = 3

f(x) = x² − 4x − 5

= 3² - 4(3) - 5

= 9 - 12 - 5

= -8

Point = (3,-8)

For x = 4

f(x) = x² − 4x − 5

= 4² - 4(4) - 5

= 16 - 16 - 5

= -5

Point = (4,-5)

For x = 5

f(x) = x² − 4x − 5

= 5² - 4(5) - 5

= 25 - 20 - 5

= 0

Point = (5,0)

For x = 6

f(x) = x² − 4x − 5

= 6² - 4(6) - 5

= 36 - 24 - 5

= 7

Point = (6,7)

Coordinates for graph = (-2,7) , (-1,0) , (0,-5) , (1,-8) , (2,-9) ,  (3,-8) ,  (4,-5) , (5,0) ,  (6,7)

These are the points to sketch the quadratic graph.