How do you write the quadratic function in intercept form given x intercepts -1,6 and point (1,-20)?

Question

1463 views around the world

You can reuse this answer
Creative Commons License

Answer 1 · 2016-10-18T00:18:29

Please see the explanation for the process.

#y = 2x^2 - 10x -12#

If -1 and 6 are the x intercepts, then (x + 1) and (x -6) are factors:

#y = k(x + 1)(x - 6)#

To find the value of k, we substitute the given point into the equation:

#-20 = k(1 + 1)(1 - 6)#

#-20 = k(2)(-5)#

#k = 2#

Use the F.O.I.L. method to do the multiplication:

#y = 2(x + 1)(x - 6)#
#y = 2(x^2 - 6x + x - 6)#
#y = 2x^2 - 10x -12#