Question

How do you graph `f(x) = 2x^2 - x - 1`?

Answer 1

Refer Explanation section

Explanation:

Given -
y = `2x^2- x − 1`

It is a U shaped curve. Since the sign of the`2x^2` is positive, it is concave upwards.
Find the vertex -
x = `(−b)/(2a)= (-(-1))/(2 xx2)= 1/4`
It means when x takes the value `1/4`, the curve turns.
Take a few values on either side of `1/4`. Calculate corresponding y values. Plot the pairs. Join them with the help of a smooth curve

x : y
-3 : 20
-2 : 9
-1 : 2
0 : -1
0.25 : -1.125
1 : 0
2 : 5
3 : 14
4 27
graph{2x^2-x-1 [-10, 10, -5, 5]}