Hey guys I'm a bit stuck on this question.
Curve intersects at (-5, 0), (-2,0), (1.5, 0) and (0, -30)
i) Express the three points of intersection as an equation in fully factorised form.
which I put =(x+5)(x+2)(2x-3)
then it said
ii) Expand the brackets to show the equation of the curve can be written as 2x3 + 11x2 - x - 30. [2]
which I did.
Then it said: draw the line y =5x+2 accurately and find the x-coordinates of the points of intersection.
and so i made x = 0 and marked y as 2 and then made y = to get x= -2/5
I then read off the x-coordinates of intersection with the curve and i got -5.39 and 1.85
But I really don't understand how to do this next part...
it says:
Show that the x-coordinates satisfy the equation 2x2 +2x - 20=0.
Hence find the exact values of the x coordinates of the other points of intersection. [5]
How do I show that my values satisfy the equation? I got decimal numbers and I can't use a calculator.
I'm so confused.