How many real solutions does the equation have?

Answer and explanation

Correct answer: B.

  1. Step 1: Let ; , so the turning points are at and . Step 2. is the local maximum and is the local minimum, both positive. Step 3. The graph crosses the -axis only once, to the left of (a cubic always has at least one real root). **Answer: . Why not the others:** : A cubic always has at least one real root. : Two roots would need a turning point on the axis, but the local minimum value is . : Three roots would need the local minimum to be below the axis.

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