Given
- The graph of cubic function y = f(x)
Find
- x such that f(x) = -2
- x such that f(x) = 0
Solution
a) For the first one (f(x) = -2), you need to draw (or imagine) a line at y = -2. Find the places where that line intersects the given curve. Note the x-coordinates of those places.
The function f(x) has the value -2 at x = -1 and at x = 2.
b) For the second one, you do something similar. You draw (or imagine) a line at y=0. (This is the x-axis.) Find the places where the curve crosses that line. They look to be about x = -1.75, x = 0, x = 1.75.
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The curve actually has zeros at 0 and ±√3 ≈ ±1.732. The answers above are "close enough" and about what you'd expect to read from a graph like this.