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Complete the table for $y = x^3 - 3x$ - OCR - GCSE Maths - Question 9 - 2018 - Paper 1

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Complete the table for $y = x^3 - 3x$. $x$ | $-3$ | $-2$ | $-1$ | $0$ | $1$ | $2$ | $3$ $y$ | $-18$ | $-2$ | $0$ | $0$ | $-2$ | $18$ | Draw the graph of... show full transcript

Worked Solution & Example Answer:Complete the table for $y = x^3 - 3x$ - OCR - GCSE Maths - Question 9 - 2018 - Paper 1

Step 1

Complete the table for $y = x^3 - 3x$.

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Answer

To complete the table, we substitute each value of xx into the equation y=x33xy = x^3 - 3x:

  • For x=3x = -3: y=(3)33(3)=27+9=18y = (-3)^3 - 3(-3) = -27 + 9 = -18
  • For x=2x = -2:
    y=(2)33(2)=8+6=2y = (-2)^3 - 3(-2) = -8 + 6 = -2
  • For x=1x = -1:
    y=(1)33(1)=1+3=2y = (-1)^3 - 3(-1) = -1 + 3 = 2
  • For x=0x = 0:
    y=033(0)=0y = 0^3 - 3(0) = 0
  • For x=1x = 1:
    y=133(1)=13=2y = 1^3 - 3(1) = 1 - 3 = -2
  • For x=2x = 2:
    y=233(2)=86=2y = 2^3 - 3(2) = 8 - 6 = 2
  • For x=3x = 3:
    y=333(3)=279=18y = 3^3 - 3(3) = 27 - 9 = 18

The completed table is as follows:

xx | 3-3 | 2-2 | 1-1 | 00 | 11 | 22 | 33
yy | 18-18 | 2-2 | 22 | 00 | 2-2 | 22 | 1818

Step 2

Draw the graph of $y = x^3 - 3x$ for $-3 \leq x \leq 3$.

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Answer

To draw the graph of the function, plot the points from the completed table:

  • Plot the points:
    (3,18)(-3, -18),
    (2,2)(-2, -2),
    (1,2)(-1, 2),
    (0,0)(0, 0),
    (1,2)(1, -2),
    (2,2)(2, 2),
    (3,18)(3, 18).

  • Connect the points smoothly, noting that the graph will have a cubic curve shape that passes through them while adhering to the established range for xx.

Step 3

Use your graph to solve $x^3 - 3x = 10$.

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Answer

To solve the equation x33x=10x^3 - 3x = 10, first rearrange it to x33x10=0x^3 - 3x - 10 = 0.

Once the graph is drawn, identify where the graph intersects the horizontal line y=10y = 10. This intersection gives the solution(s) for the equation.

From our graph, locate the intersection points:

  • Approximate the xx-values where the graph reaches y=10y = 10, which could be estimated graphically or with numerical methods, providing the roots as necessary.

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