Finding the vertex of a quadratic and the product of two complex numbers

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Discussion Overview

The discussion revolves around finding the vertex of a quadratic function and simplifying the product of two complex numbers. It includes algebraic methods and verification of answers provided by participants.

Discussion Character

  • Homework-related
  • Mathematical reasoning

Main Points Raised

  • One participant claims the vertex of the function f(x) = -2x^2 - 8x + 3 is (-2, 0).
  • Another participant calculates the vertex and arrives at (-2, 11), questioning the first participant's answer and asking for clarification on how they derived their result.
  • A third participant provides the formula x = -b/(2a) to find the x-coordinate of the vertex, showing their calculation and acknowledging a mistake in not substituting back to find y.
  • A fourth participant confirms the calculation of f(-2) and shows that it equals 11, supporting the second participant's claim.
  • For the multiplication of complex numbers, one participant states their answer as 39 - 2i, while another participant confirms this answer as correct.

Areas of Agreement / Disagreement

There is disagreement regarding the vertex of the quadratic function, with one participant asserting it is (-2, 0) and others supporting the vertex as (-2, 11). The multiplication of complex numbers appears to be agreed upon with one participant confirming the answer.

Contextual Notes

The discussion includes unresolved assumptions about the methods used to find the vertex and the implications of the calculations presented. The participants' understanding of the vertex and its calculation process is not fully aligned.

drop
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Basically I don't know anyone in real life that can help me with this, so I need help checking to see if my answers are correct :)

PART A

11) Find the vertex of f(x) = -2x^2 - 8x + 3 algebraically.

My Answer: (-2,0)

12) Multiply and simplify: (6 - 5i) (4 + 3i)

My Answer: 39 - 2i
 
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Re: Please check my answers - 6

drop said:
Basically I don't know anyone in real life that can help me with this, so I need help checking to see if my answers are correct :)

PART A

11) Find the vertex of f(x) = -2x^2 - 8x + 3 algebraically.

My Answer: (-2,0)

I get $(-2, 11)$. Now can you help me by explaining to us how did you arrive at $(-2, 0)$ as the vertex of the function of f of x?
drop said:
12) Multiply and simplify: (6 - 5i) (4 + 3i)

My Answer: 39 - 2i

Correct.:)
 
Re: Please check my answers - 6

x = -b/(2a)

x = -(-8)/2(-2)

x = 8/-4 = -2

I think I forgot to substitute -2 for x to find out y, thanks for pointing that out! (I was thinking of x intercepts) After solving for y, I got (-2,11) Thank you
 
Re: Please check my answers - 6

Yes...and as you can see, $f(-2)=-2(-2)^2-8(-2)+3=11$.
 

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