The table gives some values for $y = 2x^3 + 6x^2 - 2.5$.
$x$: -3, -2.5, -2, -1.5, -1, -0.5, 0, 0.5, 1
$y$: , 3.75, 5.5, 4.25, 1.5, , -2.5, -0.75,
(a)[3]
Complete the missing values in the table.
(b)[4]
On the grid, plot the graph of $y = 2x^3 + 6x^2 - 2.5$ for $-3 \le x \le 1$.
(c)[3]
By drawing a suitable line on the graph, solve the equation $2x^3 + 6x^2 = 4.5$.
(d)[2]
The equation $2x^3 + 6x^2 - 2.5 = k$ has exactly two solutions. Write down the two possible values of $k$.
Worked solution & mark scheme
This 12-mark question has a full step-by-step worked solution and mark scheme. One marking point: “The correct roots are $-2.5,-1.25,5.5$” …
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