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  1. Home
  2. 12th grade
  3. Precalculus
  4. Exercise : Match curves and quadratic functions

Match curves and quadratic functions Precalculus

Find the equation of the functions defined by the following graphs.

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The x-intercepts of the function are -\dfrac{1}{2} and 2, so the solutions of the equation f\left(x\right)=0 are -\dfrac{1}{2} and 2.

We can write this fact as:

\left( x+\dfrac{1}{2} \right)\left( x-2 \right)=0

Which simplifies to:

x^{2}-\dfrac{3}{2}x-1=0

The y-intercept of the function is -2, so we multiply the last equation by 2:

2\left( x^{2}-\dfrac{3}{2}x-1 \right)=0

Which simplifies to:

2x^{2}-3x-2=0

The function matching the given graph is:

f\left(x\right)=2x^{2}-3x-2

-

The x-intercepts of the function are -\dfrac{5}{2} and 1, so the solutions of the equation f\left(x\right)=0 are -\dfrac{5}{2} and 1.

We can write this fact as:

\left( x+\dfrac{5}{2} \right)\left( x-1 \right)=0

Which simplifies to:

x^{2}+\dfrac{3}{2}x-\dfrac{5}{2}=0

The y-intercept of the function is -5, so we multiply the last equation by 2:

2\left( x^{2}+\dfrac{3}{2}x-\dfrac{5}{2} \right)=0

Which simplifies to:

2x^{2}+3x-5=0

The function that matches the given graph is:

f\left(x\right)=2x^{2}+3x-5

-

The x-intercepts of the function are -2 and 3, so the solutions of the equation f\left(x\right)=0 are -2 and 3.

We can write this fact as:

\left( x+2 \right)\left( x-3 \right)=0

Which simplifies to:

x^{2}-x-6=0

The y-intercept of the function is 12, so we multiply the last equation by -2 :

-2\left( x^{2}-x-6 \right)=0

Which simplifies to:

-2x^{2}+2x+12=0

The function that matches the given graph is:

f\left(x\right)=-2x^{2}+2x+12

-

The x-intercepts of the function are -4 and \dfrac{3}{2}, so the solutions of the equation f\left(x\right)=0 are -4 and \dfrac{3}{2}.

We can write this fact as:

\left( x+4 \right)\left( x-\dfrac{3}{2} \right)=0

Which simplifies to:

x^{2}+\dfrac{5}{2}x-6=0

The y-intercept of the function is -12, so we multiply the last equation by 2:

2\left( x^{2}+\dfrac{5}{2}x-6 \right)=0

Which simplifies to:

2x^{2}+5x-12=0

The function that matches the given graph is:

f\left(x\right)=2x^{2}+5x-12

-

The x-intercepts of the function are -1 and 1, so the solutions of the equation f\left(x\right)=0 are -1 and 1.

We can write this fact as:

\left( x+1 \right)\left( x-1\right)=0

Which simplifies to:

x^{2}-1=0

The y-intercept of the function is 3, so we multiply the last equation by -3 :

-3\left( x^{2}-1 \right)=0

Which simplifies to:

-3x^{2}+3=0

The function that matches the given graph is:

f\left(x\right)=-3x^{2}+3

-

The x-intercepts of the function are -2 and \dfrac{1}{2}, so the solutions of the equation f\left(x\right)=0 are -2 and \dfrac{1}{2}.

We can write this fact as:

\left( x+2 \right)\left( x-\dfrac{1}{2}\right)=0

Which simplifies to:

x^{2}+\dfrac{3}{2}x-1=0

The y-intercept of the function is -6, so we multiply the last equation by 6:

6\left( x^{2}+\dfrac{3}{2}x-1 \right)=0

Which simplifies to:

6x^{2}+9x-6=0

The function that matches the given graph is:

f\left(x\right)=6x^{2}+9x-6

-

The x-intercepts of the function are -1 and 3, so the solutions of the equation f\left(x\right)=0 are -1 and 3.

We can write this fact as:

\left(x+1\right)\left( x-3\right)=0

Which simplifies to:

x^{2}-2x-3=0

The y-intercept of the function is 6, so we multiply the last equation by -2 :

-2\left( x^{2}-2x-3 \right)=0

Which simplifies to:

-2x^{2}+4x+6=0

The function that matches the given graph is:

f\left(x\right)=-2x^{2}+4x+6

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See also
  • Course : Quadratic functions
  • Exercise : Convert between the expanded form and the vertex form of a quadratic function
  • Exercise : Calculate the average rate of change of a quadratic function
  • Exercise : Solve quadratic equations with calculations
  • Exercise : Solve quadratic inequalities with calculations
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