Operations of Functions from Graphs

Graph of functions

Form of functions

This image shows straight line graph go upwards. So the equation must have positive x. Eg : y = x + 2 .

This image shows straight line graph go downwards. So the equation must have negative x. Eg : y = -x + 1 .

Multiple Choice

Which equations fits the graph?

• y = x + 2

• y = 3 - x

• $$y\ =\ x^{2\ }+\ 2$$
  

Parabola graph (+)

Has U shape. Must has positive x² in its equation. Eg : x² - 2 .

Parabola graph (-)

Has  $\cap\ shape\ .$  Must has negative  $x^2$  in its equation. Eg : - $x^2$ + 3

Multiple Choice

Which equation fit the graph?

• y = -x - 3

• y = -x² + 3

• y = x - 3

• y = x² + 3

Cubic graph (+)

This cubic graph goes upwards. So, it has + x³ in its equation. Eg : y = x³ + 1

Cubic graph (-)

Cubic graph goes downwards. So, in its equation, it must have -x^{3 .} Eg : y = -x³ - 2

Multiple Choice

Which equation fits the graph?

• y = x² + 3

• y = -x³ + 3

• y = x³ + 3

• y = -x² + 3