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GB-24-01-001 · Plotting quadratics

A curve has equation y=x2+3x−1y=x^{2} + 3x - 1.

(a) Complete the table.

x-3-2-10123
y

(b) On squared paper, draw the curve for −3 ≤ x ≤ 3. Use a suitable scale.

Part (a) Plotting Quadratic Graphs Booklet p. 78 & p. 88
Method
1) Sub each x-value into the quadratic using brackets ( )
2) Plot points on grid
3) Join with a smooth U-shaped parabola
Worked Example (GB-24-01-001 · Part (a))
Complete the table.
x-3-2-10123
y
1)
Substitute each x value using brackets, for example y(−3)=1(−3)2+3(−3)−1=−1y(-3)=1(-3)^2+3(-3) - 1=-1.
2)
x-3-2-10123
y-1-3-3-13917
Ans = -1, -3, -3, -1, 3, 9, 17
Part (b) Plotting Quadratic Graphs Booklet p. 78 & p. 88
Method
1) Sub each x-value into the quadratic using brackets ( )
2) Plot points on grid
3) Join with a smooth U-shaped parabola
Worked Example (GB-24-01-001 · Part (b))
On squared paper, draw the curve for −3 ≤ x ≤ 3. Use a suitable scale.
1)
Substitute each x value using brackets, for example y(−3)=1(−3)2+3(−3)−1=−1y(-3)=1(-3)^2+3(-3) - 1=-1.
2)
x-3-2-10123
y-1-3-3-13917
3)
Plot the points and join with a smooth parabola.
4)
-3-3.25-1.80.8-0.64.850.68.91.812.95317xy
Ans = Smooth parabola through (-3,-1), (-2,-3), (-1,-3), (0,-1), (1,3), (2,9), (3,17).