Number of Solutions / Roots via Curve Analysis

The question asks the student to determine the number of real solutions of an equation (or intersection points of curves) by using variation tables, the intermediate value theorem, or graphical/analytical reasoning about a function's behavior.

ap-calculus-ab 2012 Q77 View
Let $f$ be a function that is continuous on the closed interval $[ 2,4 ]$ with $f ( 2 ) = 10$ and $f ( 4 ) = 20$. Which of the following is guaranteed by the Intermediate Value Theorem?
(A) $f ( x ) = 13$ has at least one solution in the open interval $( 2,4 )$.
(B) $f ( 3 ) = 15$
(C) $f$ attains a maximum on the open interval $( 2,4 )$.
(D) $f ^ { \prime } ( x ) = 5$ has at least one solution in the open interval $( 2,4 )$.
(E) $f ^ { \prime } ( x ) > 0$ for all $x$ in the open interval $( 2,4 )$.
brazil-enem 2017 Q168 View
The Church of Saint Francis of Assisi, a modernist architectural work by Oscar Niemeyer, located at Pampulha Lake, in Belo Horizonte, has parabolic vaults. Figure 2 provides a front view of one of the vaults, with hypothetical measurements to simplify the calculations.
What is the measure of the height H, in meters, indicated in Figure 2?
(A) $\frac{16}{3}$
(B) $\frac{31}{5}$
(C) $\frac{25}{4}$
(D) $\frac{25}{3}$
(E) $\frac{75}{2}$
csat-suneung 2009 Q5 3 marks View
The figure on the right shows a circle with center at the origin O and radius 1, and the graph of a quadratic function $y = f ( x )$ passing through the point $( 0 , - 1 )$ on the coordinate plane. The equation $$\frac { 1 } { f ( x ) + 1 } - \frac { 1 } { f ( x ) - 1 } = \frac { 2 } { x ^ { 2 } }$$ has how many distinct real roots $x$? [3 points]
(1) 2
(2) 3
(3) 4
(4) 5
(5) 6
csat-suneung 2010 Q11 4 marks View
As shown in the figure, the graph of the cubic function $y = f ( x )$ is tangent to the $x$-axis at point $\mathrm { P } ( 2,0 )$ and meets the graph of the linear function $y = g ( x )$ only at point P. When $1 < f ( 0 ) < g ( 0 )$, what is the number of real roots of the equation $$f ( x ) + g ( x ) = \frac { 1 } { f ( x ) } + \frac { 1 } { g ( x ) }$$ ? [4 points]
(1) 7
(2) 6
(3) 5
(4) 4
(5) 3
csat-suneung 2012 Q21 4 marks View
A cubic function $f ( x )$ with leading coefficient 1 satisfies $f ( - x ) = - f ( x )$ for all real numbers $x$. When the equation $| f ( x ) | = 2$ has exactly 4 distinct real roots, what is the value of $f ( 3 )$? [4 points]
(1) 12
(2) 14
(3) 16
(4) 18
(5) 20
csat-suneung 2012 Q12 3 marks View
The graphs of the quadratic function $y = f ( x )$ and the cubic function $y = g ( x )$ are shown in the figure.
$f ( - 1 ) = f ( 3 ) = 0$, and the function $g ( x )$ has a local minimum value of $- 2$ at $x = 3$. What is the number of distinct real roots of the equation $\frac { g ( x ) + 2 } { f ( x ) } - \frac { 2 } { g ( x ) } = 1$? [3 points]
(1) 1
(2) 2
(3) 3
(4) 4
(5) 5
csat-suneung 2014 Q10 3 marks View
As shown in the figure, the graphs of function $f ( x )$ defined on the closed interval $[ - 4,4 ]$ and function $g ( x ) = - \frac { 1 } { 2 } x + 1$ meet at three points, and the $x$-coordinates of these three points are $\alpha , \beta , 2$. The inequality $$\frac { g ( x ) } { f ( x ) } \leq 1$$ is satisfied. How many integers $x$ satisfy this inequality? (Here, $- 4 < \alpha < - 3,0 < \beta < 1$) [3 points]
(1) 1
(2) 2
(3) 3
(4) 4
(5) 5
csat-suneung 2016 Q12 3 marks View
Consider the function $$f ( x ) = \begin{cases} | 5 x ( x + 2 ) | & ( x < 0 ) \\ | 5 x ( x - 2 ) | & ( x \geq 0 ) \end{cases}$$ What is the number of distinct real roots of the irrational equation $\sqrt { 4 - f ( x ) } = 1 - x$? [3 points]
(1) 1
(2) 2
(3) 3
(4) 4
(5) 5
csat-suneung 2023 Q19 3 marks View
Find the number of integers $k$ such that the equation $2 x ^ { 3 } - 6 x ^ { 2 } + k = 0$ has exactly 2 distinct positive real roots. [3 points]
gaokao 2015 Q7 View
7. As shown in the figure, the graph of function $f ( x )$ is the broken line $A C B$. The solution set of the inequality $f ( x ) \geqslant \log _ { 2 } ( x + 1 )$ is [Figure]
A. $\{ x \mid - 1 < x \leqslant 0 \}$
B. $\{ x \mid - 1 \leqslant x \leqslant 1 \}$
C. $\{ x \mid - 1 < x \leqslant 1 \}$
D. $\{ x \mid - 1 < x \leqslant 2 \}$
gaokao 2015 Q13 View
13. The number of zeros of the function $f ( x ) = 2 \sin x \sin \left( x + \frac { \pi } { 2 } \right) - x ^ { 2 }$ is $\_\_\_\_$.
gaokao 2015 Q12 View
12. The number of zeros of the function $f(x) = 4\cos^2\frac{x}{2}\cos\left(\frac{\pi}{2} - x\right) - 2\sin x - |\ln(x+1)|$ is $\_\_\_\_$ .
gaokao 2015 Q14 View
14. If the function $f ( x ) = \left| 2 ^ { x } - 2 \right| - b$ has two zeros, then the range of the real number $b$ is $\_\_\_\_$
gaokao 2015 Q15 View
15. Given the function $\mathrm { f } ( \mathrm { x } ) = \left\{ \begin{array} { l l } x ^ { 3 } , & \mathrm { x } \leq \mathrm { a } , \\ \mathrm { x } ^ { 2 } , & \mathrm { x } > \mathrm { a } , \end{array} \right.$ if there exists a real number $b$ such that the function $\mathrm { g } ( \mathrm { x } ) = \mathrm { f } ( \mathrm { x } ) - \mathrm { b }$ has exactly two zeros, then the range of values for $a$ is $\_\_\_\_$.
III. Solution Questions: This section has 6 questions, for a total of 75 points. Show your work, proofs, or calculation steps in your answers.
gaokao 2015 Q13 View
13. Given functions $f ( x ) = | \ln x | , g ( x ) = \left\{ \begin{array} { c } 0,0 < x \leq 1 \\ \left| x ^ { 2 } - 4 \right| - 2 , x > 1 \end{array} \right.$, then the number of real roots of the equation $| f ( x ) + g ( x ) | = 1$ is $\_\_\_\_$.
gaokao 2015 Q8 View
8. Given the function $f ( x ) = \begin{cases} 2 - | x | , & x \leq 2 \\ ( x - 2 ) ^ { 2 } , & x > 2 \end{cases}$, and function $g ( x ) = 3 - f ( 2 - x )$, then the number of intersections of the graphs of $y = f(x)$ and $y = g(x)$ is
(A) 2
(B) 3
(C) 4
(D) 5
II. Fill-in-the-Blank Questions: This section has 6 questions, each worth 5 points, for a total of 30 points.
gaokao 2015 Q8 5 marks View
Given the function $F(x) = \left\{\begin{array}{l}2 - |x|, \quad x \leq 2 \\ (x - 2)^2, \quad x > 2\end{array}\right.$ and function $g(x) = b - f(2 - x)$, where $b \in \mathbb{R}$. If the function $y = f(x) - g(x)$ has exactly 4 zeros, then the range of $b$ is
(A) $\left(\frac{7}{4}, +\infty\right)$
(B) $\left(-\infty, \frac{7}{4}\right)$
(C) $\left(0, \frac{7}{4}\right)$
(D) $\left(\frac{7}{4}, 2\right)$
gaokao 2018 Q9 5 marks View
Given the function $f ( x ) = \left\{ \begin{array} { l l } \mathrm { e } ^ { x } , & x \leqslant 0 , \\ \ln x , & x > 0 , \end{array} \right.$ and $g ( x ) = f ( x ) + x + a$. If $g ( x )$ has 2 zeros, then the range of $a$ is
A. $( 0 , + \infty )$
B. $[ 0 , + \infty )$
C. $[ - 1 , + \infty )$
D. $[ 1 , + \infty )$
gaokao 2023 Q10 5 marks View
Let $f(x)$ be the function obtained by shifting $y = \cos\left(2x + \frac{\pi}{4}\right)$ to the left by $\frac{\pi}{6}$ units. The number of intersection points of $y = f(x)$ and $y = \frac{1}{2}x - \frac{1}{2}$ is
A. $1$
B. $2$
C. $3$
D. $4$
gaokao 2024 Q6 5 marks View
Let $f ( x ) = a ( x + 1 ) ^ { 2 } - 1 , g ( x ) = \cos x + 2 a x$. When $x \in ( - 1,1 )$, the curves $y = f ( x )$ and $y = g ( x )$ have exactly one intersection point. Then $a =$
A. $- 1$
B. $\frac { 1 } { 2 }$
C. 1
D. 2
grandes-ecoles 2018 Q31 View
Deduce that for all $x \in [0, 1[$
$$1 + \exp\left(\frac{x^{2}}{2}\right)(1 - x)^{x - 1} \leqslant \frac{4}{2 - x}$$
grandes-ecoles 2018 Q31 View
Deduce that for all $x \in [0, 1[$
$$1 + \exp\left(\frac{x^{2}}{2}\right)(1 - x)^{x - 1} \leqslant \frac{4}{2 - x}$$
grandes-ecoles 2020 Q10 View
Let $f(x) = xe^x$, and let $V$ and $W$ denote the inverses of $f|_{]-\infty,-1]}$ and $f|_{[-1,+\infty[}$ respectively. For a real parameter $m$, we consider the inequality with unknown $x \in \mathbb { R }$
$$x \mathrm { e } ^ { x } \leqslant m \tag{I.2}$$
Using the functions $V$ and $W$, determine, according to the values of $m$, the solutions of (I.2). Illustrate graphically the different cases.
grandes-ecoles 2020 Q11 View
Let $V$ and $W$ denote the inverses of $f|_{]-\infty,-1]}$ and $f|_{[-1,+\infty[}$ respectively, where $f(x) = xe^x$. For non-zero real parameters $a$ and $b$, we consider the equation with unknown $x \in \mathbb { R }$
$$\mathrm { e } ^ { a x } + b x = 0 \tag{I.3}$$
Determine, according to the values of $a$ and $b$, the number of solutions of (I.3). Explicitly express the possible solutions using the functions $V$ and $W$.
isi-entrance 2012 Q3 View
Find the number of intersection points of $y = \log x$ and $y = x^2$.