hb wrote:
Thank you for the explanation. This is more clear to me now. The above is a quadratic equation with one variable. This may seem a very basic question as I have not plotted the quadratic equation myself yet. But can we plot an equation with one variable on a two variable axis ?
You can plot something like
y=x^2+5x-15=> it's a parabola.
You then can read the graph in this way:
1)where it intersects the x-axis the equation has its root(s).
2)if you are asked y=x^2+5x-15>0, you'll pick the "parts"/range of values for x where the graph is positive or over the y-axis.
3)if you are asked y=x^2+5x-15<0, you'll pick the part where the graph is below the y-axis.
4)if you are asked y=x^2+5x-15=0, you'll pick the single point(s) where the graph intersect the y axis.