How to add a expression like this

[JENIL_Sarvaiya]

i have been following a script but could figure out to add such can someone helpme
Its an important part to add up

[JENIL_Sarvaiya]

expression - x(x+1)R

[John_Brock]

Assigned to Grasshopper category.

[Tom_P]

doubleclick on the canvas.
in the searchfield write
expression
you should get a component like this - the expression component:

zoom in to delete and edit parameters / input / output
(change “Variable x” to x, delete Variable y)

doubleclick on the formula and replace it with x+1

[JENIL_Sarvaiya]

thankyou it worked