y = x2 - 2x - 3
On the grid, draw the graph of y = x2 - 2x - 3 for values of x from -3 to 3.
Worked Solution & Answer
y = 12, 5, 0, -3, -4, -3, 0
Home > Maths quizzes > Grade 5 Quizzes > Drawing quadratic graphs
Grade 5 • 5J • 10 Questions (30 Marks)
Explanation:
A quadratic graph y = ax2 + bx + c is a smooth, symmetrical U-shaped curve called a parabola (or ∩-shaped if a is negative). When substituting negative values into x2, always use brackets: squaring a negative number gives a positive answer, e.g. (−2)2 = +4.
Plot each (x, y) point from your table and join them with a single smooth curve (never connect points with straight ruler lines). The bottom of the curve is the minimum turning point, and the points where it crosses the x-axis (y = 0) are the roots.
Example 1: Complete the table for y = x2 − 2x − 3.
Solution:
| x | −2 | −1 | 0 | 1 | 2 | 3 | 4 |
|---|---|---|---|---|---|---|---|
| y | 5 | 0 | −3 | −4 | −3 | 0 | 5 |
Example 2: From the graph of y = x2 − 2x − 3, find (a) the turning point and (b) the roots of x2 − 2x − 3 = 0.
Solution: