How many real solutions does the equation have?
Answer and explanation
Correct answer: B.
- 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.
Practise more Applications of differentiation.
Free questions with an explanation for every one, and full timed Pancyprian Examinations (Cyprus) mock tests.
More Applications of differentiation questions
- Find the -coordinates of the stationary points of .
- On which interval is strictly decreasing?
- What is the local maximum value of ?
- Where is the point of inflection of the graph of ?
- Find the greatest and least values of on the interval .
- A square sheet of side cm has a square of side cm cut from each corner, and the sides are folded up to form an open box. What is th…