Answer:
![\textsf{A)} \quad x=-2, \:\:x=\dfrac{5}{2}](https://tex.z-dn.net/?f=%5Ctextsf%7BA%29%7D%20%5Cquad%20x%3D-2%2C%20%5C%3A%5C%3Ax%3D%5Cdfrac%7B5%7D%7B2%7D)
![\textsf{B)} \quad \left(\dfrac{1}{4},-\dfrac{81}{8}\right)=(0.25,-10.125)](https://tex.z-dn.net/?f=%5Ctextsf%7BB%29%7D%20%5Cquad%20%5Cleft%28%5Cdfrac%7B1%7D%7B4%7D%2C-%5Cdfrac%7B81%7D%7B8%7D%5Cright%29%3D%280.25%2C-10.125%29)
C) See attachment.
Step-by-step explanation:
Given function:
![f(x)=2x^2-x-10](https://tex.z-dn.net/?f=f%28x%29%3D2x%5E2-x-10)
<h3><u>Part A</u></h3>
To factor a <u>quadratic</u> in the form
<em> , </em>find two numbers that multiply to
and sum to
:
![\implies ac=2 \cdot -10=-20](https://tex.z-dn.net/?f=%5Cimplies%20ac%3D2%20%5Ccdot%20-10%3D-20)
![\implies b=-1](https://tex.z-dn.net/?f=%5Cimplies%20b%3D-1)
Therefore, the two numbers are -5 and 4.
Rewrite
as the sum of these two numbers:
![\implies f(x)=2x^2-5x+4x-10](https://tex.z-dn.net/?f=%5Cimplies%20f%28x%29%3D2x%5E2-5x%2B4x-10)
Factor the first two terms and the last two terms separately:
![\implies f(x)=x(2x-5)+2(2x-5)](https://tex.z-dn.net/?f=%5Cimplies%20f%28x%29%3Dx%282x-5%29%2B2%282x-5%29)
Factor out the common term (2x - 5):
![\implies f(x)=(x+2)(2x-5)](https://tex.z-dn.net/?f=%5Cimplies%20f%28x%29%3D%28x%2B2%29%282x-5%29)
The x-intercepts are when the curve crosses the x-axis, so when y = 0:
![\implies (x+2)(2x-5)=0](https://tex.z-dn.net/?f=%5Cimplies%20%28x%2B2%29%282x-5%29%3D0)
Therefore:
![\implies (x+2)=0 \implies x=-2](https://tex.z-dn.net/?f=%5Cimplies%20%28x%2B2%29%3D0%20%5Cimplies%20x%3D-2)
![\implies (2x-5)=0 \implies x=\dfrac{5}{2}](https://tex.z-dn.net/?f=%5Cimplies%20%282x-5%29%3D0%20%5Cimplies%20x%3D%5Cdfrac%7B5%7D%7B2%7D)
So the x-intercepts are:
![x=-2, \:\:x=\dfrac{5}{2}](https://tex.z-dn.net/?f=x%3D-2%2C%20%5C%3A%5C%3Ax%3D%5Cdfrac%7B5%7D%7B2%7D)
<h3><u>Part B</u></h3>
The x-value of the vertex is:
![\implies x=\dfrac{-b}{2a}](https://tex.z-dn.net/?f=%5Cimplies%20x%3D%5Cdfrac%7B-b%7D%7B2a%7D)
Therefore, the x-value of the vertex of the given function is:
![\implies x=\dfrac{-(-1)}{2(2)}=\dfrac{1}{4}](https://tex.z-dn.net/?f=%5Cimplies%20x%3D%5Cdfrac%7B-%28-1%29%7D%7B2%282%29%7D%3D%5Cdfrac%7B1%7D%7B4%7D)
To find the y-value of the vertex, substitute the found value of x into the function:
![\implies f\left(\dfrac{1}{4}\right)=2\left(\dfrac{1}{4}\right)^2-\left(\dfrac{1}{4}\right)-10=-\dfrac{81}{8}](https://tex.z-dn.net/?f=%5Cimplies%20f%5Cleft%28%5Cdfrac%7B1%7D%7B4%7D%5Cright%29%3D2%5Cleft%28%5Cdfrac%7B1%7D%7B4%7D%5Cright%29%5E2-%5Cleft%28%5Cdfrac%7B1%7D%7B4%7D%5Cright%29-10%3D-%5Cdfrac%7B81%7D%7B8%7D)
Therefore, the vertex of the function is:
![\left(\dfrac{1}{4},-\dfrac{81}{8}\right)=(0.25,-10.125)](https://tex.z-dn.net/?f=%5Cleft%28%5Cdfrac%7B1%7D%7B4%7D%2C-%5Cdfrac%7B81%7D%7B8%7D%5Cright%29%3D%280.25%2C-10.125%29)
<h3><u>Part C</u></h3>
Plot the x-intercepts found in Part A.
Plot the vertex found in Part B.
As the <u>leading coefficient</u> of the function is positive, the parabola will open upwards. This is confirmed as the vertex is a minimum point.
The axis of symmetry is the <u>x-value</u> of the <u>vertex</u>. Draw a line at x = ¹/₄ and use this to ensure the drawing of the parabola is <u>symmetrical</u>.
Draw a upwards opening parabola that has a minimum point at the vertex and that passes through the x-intercepts (see attachment).