maths(about reading information from graphs)

When the graph y=kx^2-x-5 has no interception with the x-axis, it means that the equation when y =0 i.e. kx^2-x-5 =0 has no real roots.

(-1)^2 - 4k(-5) is less than 0

1 + 20k is less than 0

20k is less than -1

k is less than -1/20

2006-10-24 08:28:02 補充：
kx^2-x-5 =0 has no real roots means the discriminant of this equation is less than 0. Discriminant of this equation = (-1)^2 - 4k(-5) i.e. (-1)^2 - 4k(-5) is less than 0

find D < 0 where D = b^2 - 4ac, for the equation ax^2 + bx + c

in this case (-1)^2 -4(k)(-5) < 0
20k < -1
k < -1/20

k < -1/20 will give no solution, meaning x-intercept

< mean small than. dont know why it cant show

hope it acn help