Find range where function increasing/decreasing

A question is this type if and only if it asks to find the set of values of x (or range) for which a given function is increasing or decreasing, requiring solving an inequality involving the derivative.

30 questions · Moderate -0.4

1.07o Increasing/decreasing: functions using sign of dy/dx
Sort by: Default | Easiest first | Hardest first
CAIE P1 2020 March Q1
3 marks Standard +0.3
1 The function f is defined by \(\mathrm { f } ( x ) = \frac { 1 } { 3 x + 2 } + x ^ { 2 }\) for \(x < - 1\).
Determine whether f is an increasing function, a decreasing function or neither.
Edexcel C12 2017 January Q1
7 marks Moderate -0.8
Given \(y = \frac { x ^ { 3 } } { 3 } - 2 x ^ { 2 } + 3 x + 5\)
  1. find \(\frac { \mathrm { d } y } { \mathrm {~d} x }\), simplifying each term.
  2. Hence find the set of values of \(x\) for which \(\frac { \mathrm { d } y } { \mathrm {~d} x } > 0\)
Edexcel P2 2019 October Q1
6 marks Moderate -0.8
  1. A curve \(C\) has equation \(y = 2 x ^ { 2 } ( x - 5 )\)
    1. Find, using calculus, the \(x\) coordinates of the stationary points of \(C\).
    2. Hence find the values of \(x\) for which \(y\) is increasing.
Edexcel P2 2021 October Q8
10 marks Standard +0.2
8. In this question you must show all stages of your working. Solutions relying entirely on calculator technology are not acceptable. \begin{figure}[h]
\includegraphics[alt={},max width=\textwidth]{124ee19f-8a49-42df-9f4b-5a1cc2139be9-24_739_736_411_605} \captionsetup{labelformat=empty} \caption{Figure 2}
\end{figure} Figure 2 shows a sketch of part of the curve \(C\) with equation $$y = \frac { 4 } { 3 } x ^ { 3 } - 11 x ^ { 2 } + k x \quad \text { where } k \text { is a constant }$$ The point \(M\) is the maximum turning point of \(C\) and is shown in Figure 2.
Given that the \(x\) coordinate of \(M\) is 2
  1. show that \(k = 28\)
  2. Determine the range of values of \(x\) for which \(y\) is increasing. The line \(l\) passes through \(M\) and is parallel to the \(x\)-axis.
    The region \(R\), shown shaded in Figure 2, is bounded by the curve \(C\), the line \(l\) and the \(y\)-axis.
  3. Find, by algebraic integration, the exact area of \(R\).
OCR C1 2006 January Q6
11 marks Moderate -0.8
6
  1. Find the coordinates of the stationary points on the curve \(y = x ^ { 3 } - 3 x ^ { 2 } + 4\).
  2. Determine whether each stationary point is a maximum point or a minimum point.
  3. For what values of \(x\) does \(x ^ { 3 } - 3 x ^ { 2 } + 4\) increase as \(x\) increases?
OCR C1 2007 January Q8
11 marks Moderate -0.3
8
  1. Find the coordinates of the stationary points of the curve \(y = 27 + 9 x - 3 x ^ { 2 } - x ^ { 3 }\).
  2. Determine, in each case, whether the stationary point is a maximum or minimum point.
  3. Hence state the set of values of \(x\) for which \(27 + 9 x - 3 x ^ { 2 } - x ^ { 3 }\) is an increasing function. \(9 \quad A\) is the point \(( 2,7 )\) and \(B\) is the point \(( - 1 , - 2 )\).
OCR C1 2008 January Q8
11 marks Moderate -0.8
8
  1. Find the coordinates of the stationary points on the curve \(y = x ^ { 3 } + x ^ { 2 } - x + 3\).
  2. Determine whether each stationary point is a maximum point or a minimum point.
  3. For what values of \(x\) does \(x ^ { 3 } + x ^ { 2 } - x + 3\) decrease as \(x\) increases?
OCR C1 Q3
5 marks Moderate -0.3
3. $$f ( x ) = x ^ { 3 } + 4 x ^ { 2 } - 3 x + 7$$ Find the set of values of \(x\) for which \(\mathrm { f } ( x )\) is increasing.
OCR MEI C2 2007 January Q7
3 marks Moderate -0.8
7 The gradient of a curve is given by \(\frac { \mathrm { d } y } { \mathrm {~d} x } = x ^ { 2 } - 6 x\). Find the set of values of \(x\) for which \(y\) is an increasing function of \(x\).
OCR MEI C2 2009 June Q6
5 marks Moderate -0.8
6 Use calculus to find the \(x\)-coordinates of the turning points of the curve \(y = x ^ { 3 } - 6 x ^ { 2 } - 15 x\). Hence find the set of values of \(x\) for which \(x ^ { 3 } - 6 x ^ { 2 } - 15 x\) is an increasing function.
OCR MEI C2 Q2
5 marks Moderate -0.3
2 Use calculus to find the set of values of \(x\) for which \(x ^ { 3 } - 6 x\) is an increasing function.
OCR MEI C2 Q9
3 marks Moderate -0.5
9 Use calculus to find the set of values of \(x\) for which \(\mathrm { f } ( x ) = 12 x - x ^ { 3 }\) is an increasing function.
OCR MEI C2 Q5
5 marks Moderate -0.5
5 Use calculus to find the \(x\)-coordinates of the turning points of the curve \(y = x ^ { 3 } - 6 x ^ { 2 } - 15 x\). Hence find the set of values of \(x\) for which \(x ^ { 3 } - 6 x ^ { 2 } - 15 x\) is an increasing function.
OCR C1 2010 June Q10
14 marks Standard +0.3
10
  1. Find the coordinates of the stationary points of the curve \(y = 2 x ^ { 3 } + 5 x ^ { 2 } - 4 x\).
  2. State the set of values for \(x\) for which \(2 x ^ { 3 } + 5 x ^ { 2 } - 4 x\) is a decreasing function.
  3. Show that the equation of the tangent to the curve at the point where \(x = \frac { 1 } { 2 }\) is \(10 x - 4 y - 7 = 0\).
  4. Hence, with the aid of a sketch, show that the equation \(2 x ^ { 3 } + 5 x ^ { 2 } - 4 x = \frac { 5 } { 2 } x - \frac { 7 } { 4 }\) has two distinct real roots.
OCR C1 2012 June Q8
8 marks Moderate -0.8
8
  1. Find the coordinates of the stationary point on the curve \(y = x ^ { 4 } + 32 x\).
  2. Determine whether this stationary point is a maximum or a minimum.
  3. For what values of \(x\) does \(x ^ { 4 } + 32 x\) increase as \(x\) increases?
OCR MEI C2 2012 January Q3
3 marks Moderate -0.8
3 Find the set of values of \(x\) for which \(x ^ { 2 } - 7 x\) is a decreasing function.
OCR MEI C2 2015 June Q5
5 marks Moderate -0.3
5 Use calculus to find the set of values of \(x\) for which \(x ^ { 3 } - 6 x\) is an increasing function.
Edexcel AS Paper 1 2019 June Q5
5 marks Moderate -0.3
  1. A curve has equation
$$y = 3 x ^ { 2 } + \frac { 24 } { x } + 2 \quad x > 0$$
  1. Find, in simplest form, \(\frac { \mathrm { d } y } { \mathrm {~d} x }\)
  2. Hence find the exact range of values of \(x\) for which the curve is increasing.
Edexcel AS Paper 1 2023 June Q1
6 marks Moderate -0.8
  1. A curve has equation
$$y = \frac { 2 } { 3 } x ^ { 3 } - \frac { 7 } { 2 } x ^ { 2 } - 4 x + 5$$
  1. Find \(\frac { \mathrm { d } y } { \mathrm {~d} x }\) writing your answer in simplest form.
  2. Hence find the range of values of \(x\) for which \(y\) is decreasing.
Edexcel AS Paper 1 Specimen Q1
6 marks Moderate -0.8
  1. A curve has equation
$$y = 2 x ^ { 3 } - 2 x ^ { 2 } - 2 x + 8$$
  1. Find \(\frac { \mathrm { d } y } { \mathrm {~d} x }\)
  2. Hence find the range of values of \(x\) for which \(y\) is increasing. Write your answer in set notation.
    VIIIV SIHI NI JIIYM IONOOVIUV SIHI NI JIIAM ION OOVI4V SIHI NI JIIIM I ON OO
OCR MEI AS Paper 1 2019 June Q10
7 marks Moderate -0.3
10 In this question you must show detailed reasoning.
  1. Sketch the gradient function for the curve \(y = 24 x - 3 x ^ { 2 } - x ^ { 3 }\).
  2. Determine the set of values of \(x\) for which \(24 x - 3 x ^ { 2 } - x ^ { 3 }\) is decreasing.
OCR MEI AS Paper 2 2024 June Q13
5 marks Moderate -0.8
13 Determine the range of values of \(x\) for which \(y = 4 x ^ { 3 } + 7 x ^ { 2 } - 6 x + 8\) is a decreasing function.
AQA C1 2012 June Q7
15 marks Moderate -0.8
7 The gradient, \(\frac { \mathrm { d } y } { \mathrm {~d} x }\), of a curve \(C\) at the point \(( x , y )\) is given by $$\frac { \mathrm { d } y } { \mathrm {~d} x } = 20 x - 6 x ^ { 2 } - 16$$
    1. Show that \(y\) is increasing when \(3 x ^ { 2 } - 10 x + 8 < 0\).
    2. Solve the inequality \(3 x ^ { 2 } - 10 x + 8 < 0\).
  1. The curve \(C\) passes through the point \(P ( 2,3 )\).
    1. Verify that the tangent to the curve at \(P\) is parallel to the \(x\)-axis.
    2. The point \(Q ( 3 , - 1 )\) also lies on the curve. The normal to the curve at \(Q\) and the tangent to the curve at \(P\) intersect at the point \(R\). Find the coordinates of \(R\).
      (7 marks)
Edexcel C2 Q2
5 marks Moderate -0.3
2. $$f ( x ) = x ^ { 3 } + 4 x ^ { 2 } - 3 x + 7$$ Find the set of values of \(x\) for which \(\mathrm { f } ( x )\) is increasing.
CAIE P1 2024 November Q9
8 marks Standard +0.3
The equation of a curve is \(y = 4 + 5x + 6x^2 - 3x^3\).
  1. Find the set of values of \(x\) for which \(y\) decreases as \(x\) increases. [4]
  2. It is given that \(y = 9x + k\) is a tangent to the curve. Find the value of the constant \(k\). [4]