How is the distance to the x-axis related to the roots of quadratic equations?

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Discussion Overview

The discussion revolves around the relationship between the roots of quadratic equations and their distance from the x-axis. Participants explore concepts related to the quadratic formula and the geometric interpretation of roots and the vertex of the parabola represented by the quadratic function.

Discussion Character

  • Exploratory
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant asks how the roots of a quadratic equation relate to the distance from the x-axis at the roots, suggesting a need for clarification on this relationship.
  • Another participant points out that a root of an equation is where y=0, implying that the distance from the x-axis at the roots is zero since the graph crosses the axis there.
  • A participant later clarifies that they might be referring to the distance from the vertex of the parabola to the x-axis, rather than the roots themselves.
  • There is a mention of a specific quadratic function, y=2x^2-3x+2, with a participant noting that it has no real roots, which raises questions about the interpretation of distance in relation to complex roots.
  • Another participant discusses the distance from the vertex to the x-axis, providing a mathematical expression derived from completing the square, and connects this distance to the value of x that satisfies the equation.

Areas of Agreement / Disagreement

Participants express differing interpretations of the original question, with some focusing on the roots and others on the vertex. There is no consensus on the exact relationship being sought, and the discussion remains unresolved regarding the interpretation of distance in this context.

Contextual Notes

There are unresolved assumptions regarding the definitions of distance in relation to the roots and vertex of the quadratic function, as well as the implications of complex roots on the discussion.

lmamaths
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Hi,

How is the roots of a quadratic equation related
to the distance from the x-axis at where
the root is -
where ...
ax^2+bx+c=0
and ...
x = (-b +- SQRT(b^2-4ac))/2

Can someone help me to establish where this
distance relationship to the x-axis and the root
come from?

Thx!
LMA
 
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Am I understanding this correctly? Are you asking how the roots of a quadratic equation relate to "the distance from the x-axis at where the root is"? A root of an equation, by definition, is a point where y= 0. if y=0, then the distance from the x-axis is 0: the graph crosses the axis there!
 
Hi,

Maybe I mean't lowest part of the curve to the x-axis, consider:
y=2x^2-3x+2

Thx!
Leo
 
lmamaths said:
Hi,

Maybe I mean't lowest part of the curve to the x-axis, consider:
y=2x^2-3x+2

Thx!
Leo

I'm not really sure what you're asking Leo. That function has no real roots. If you extend the domain to complex numbers then the function is still zero (both real and imaginary parts) at each of its complex zeros. Real or complex the function is still zero at it's zero's.
 
lmamaths said:
Hi,

Maybe I mean't lowest part of the curve to the x-axis, consider:
y=2x^2-3x+2

Thx!
Leo


Ah- distance from the vertex to the x-axis.

Given y= ax2+ bx+ c= 0, consider solving by completing the square: write this as a(x2+ (b/a)x+ b2/4a2)+ c- 4b2/a= a(x- (b/2a))2+ c- 4b2/a.

The distance from the x-axis to the vertex is given when x = b/2a and is
c- 4b2/a. do you see how that is connected to the value of x that satisfies the equation?
 

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