Functions and quadratic equations

In summary, the first part of the conversation establishes that if x=2 is a root of ax^2 - bx -x = 0, then the relationship between a, b, and c is 4a - 2b - c = 0. The second part of the conversation confirms that this relationship still holds for the equation bx^2 + cx - 8a = 0, where x=2 is also a root. This is shown by multiplying the previous relationship by -2, resulting in -8a + 4b + 2c = 0, which is the same as the second equation.
  • #1
denian
641
0
if x=2 is a root of ax^2 - bx -x = 0, state the relationship connecting a,b, c and show that x=2 is also a root of
bx^2 + cx - 8a = 0.

the answer for the first part of the question is
4a - 2b - c = 0.

i need to know how to prove for the second part.
 
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  • #2
bx2 + cx - 8a = 0 ?
I can get bx2 + 2cx - 8a = 0 ...
 
  • #3
i do not type wrongly. however, can u tell me how you get that?
 
  • #4
Originally posted by denian
i do not type wrongly
if x=2 is a root of ax^2 - bx -x = 0, state the relationship connecting a,b, c

am I mean or what

anyway, I just multiplied your last result with -2. and yes, you were right, I was mistaken in the last post. It is
bx2 + cx - 8a = 0

I just get out of a meeting
 
Last edited:
  • #5
i still can't get what you mean.
 
  • #6
Originally posted by denian
the answer for the first part of the question is
4a - 2b - c = 0.

if you multiply by -2 you get
-8a + 4b + 2c = 0

show that x=2 is also a root of
bx^2 + cx - 8a = 0.

now did you get it?
 
  • #7
tq. now i know what you mean.
 

FAQ: Functions and quadratic equations

What is a function?

A function is a mathematical relationship between an input and an output. It takes in a value or set of values as input and produces a corresponding output. A function can be represented in various ways, such as an equation, table, or graph.

How do you determine if an equation is a function?

To determine if an equation is a function, you can use the vertical line test. This involves drawing a vertical line on a graph and seeing if it crosses the graph at more than one point. If it does, then the equation is not a function. Alternatively, you can also check if each input has a unique output in a table of values or by solving for y in the equation.

What is a quadratic equation?

A quadratic equation is an equation in the form of ax^2 + bx + c = 0, where a, b, and c are constants and x is the variable. It represents a parabola on a graph and has a degree of 2. Quadratic equations can have two solutions, one solution, or no real solutions depending on the value of the discriminant, b^2 - 4ac.

How do you solve a quadratic equation?

To solve a quadratic equation, you can use the quadratic formula, x = (-b ± √(b^2 - 4ac)) / 2a, where a, b, and c are the coefficients in the equation. You can also factor the equation or complete the square to find the solutions. Additionally, you can use a graphing calculator to find the x-intercepts of the parabola.

What are the applications of quadratic equations?

Quadratic equations have many real-world applications, such as finding the maximum or minimum value of a quantity, predicting the path of a projectile, and determining the optimal shape for certain structures. They are also used in fields like engineering, physics, and economics to model and solve various problems.

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