How do you find the roots, real and imaginary, of #y= x^2 - 8x + 15 # using the quadratic formula?

1 Answer
Dec 6, 2015

Answer:

Apply the quadratic formula to find that the roots are #x=3# and #x=5#.

Explanation:

The quadratic formula states that
#ax^2 + bx+c = 0 => x = (-b+-sqrt(b^2-4ac))/(2a)#
Note that the solutions to #x# for the initial equation are the roots of
#f(x) = ax^2 + bx + c#.

Applying that here, we get
#x^2 - 8x + 15 = 0#

#=> x = (-(-8) +- sqrt( (-8)^2-4(15)(1)))/(2(1))#

#= (8+-sqrt(4))/2#

#= 4+-1#

Thus the roots are #x=3# and #x=5#.