There are equations where the graphed line would never pass over the 'y' axis, giving no solutions where 'y'=0.
Clearly I don't understand much about quadratic equations (or math in general), so please answer in stupid-people language.
2006-09-30 06:15:26 · 3 answers · asked by Ping 3 in Science & Mathematics ➔ Mathematics
y is set to zero in order to find the roots of the quadratic equation. The graph crosses the x-axis when y=o and the roots are found at the points where the crosses occur. When y is set to zero but the graph never crosses the x-axis, the roots contain imaginary components.
2006-09-30 06:20:57 · answer #1 · answered by Greg G 5 · 2⤊ 0⤋
Actually, quadratic equations always cross the Y axis, sometimes they don't cross the X axis.
Like the previous poster pointed out, quadratic equations are set to 0 to find where the graph crosses the X axis (aka "finding the roots"). If the equation never crosses the X axis (like y = x^2 + 2), the solutions are imaginary numbers.
2006-09-30 06:32:46 · answer #2 · answered by Joe C 3 · 1⤊ 0⤋
You set y=0 to find the roots- those values of x for which the curve of the equation crosses the x axis. There can be 0, 1 or 2 real answers. For the general form
y=a*x^2+b*x+c
if b^2-4*a*c>0 there are 2 real answers
if b^2-4*a*c=0 there is 1 answer (or to that are = to each other.
if b^2-4*a*c<0 there are no real answers
2006-09-30 09:27:04 · answer #3 · answered by yupchagee 7 · 1⤊ 0⤋