SEARCH HOME
Math CentralQuandaries & Queries

search

)

Question from sadiya, a student:

Find the quadratic equation whose roots are -4 and 7

Hi Sadiya,

Suppose you were given the quadratic equation

\[x^2 + 3x - 10 = 0\]

and you were asked to find the roots. I expect you would factor the quadratic to get

\[(x - 2)(x + 5) = 0\]

and then conclude that the roots are $2$ and $-5.$

If you know the roots are $2$ and $-5$ can you trace the steps backwards to obtain the quadratic equation

\[x^2 + 3x - 10 = 0?\]

Is this the only quadratic equation with roots $2$ and $-5?$ What about

\[7(x^2 + 3x - 10) = 0\]

or

\[-8(x^2 + 3x - 10) = 0\]

or

\[k(x^2 + 3x - 10) = 0\]

where $k$ is any constant?

Penny

About Math Central
 

 


Math Central is supported by the University of Regina and the Imperial Oil Foundation.
Quandaries & Queries page Home page University of Regina