Question

Illustrate the use of the quadratic formula to solve the same equation: x² + 6x + 9 = 25

Answer 1

x^2 + 6x + 9 = 25

we want this in this form : ax^2 + bx + c = 0
so we will put it in that form

x^2 + 6x + 9 = 25 --- subtract 25 from both sides
x^2 + 6x + 9 - 25 = 0 -- combine like terms
x^2 + 6x - 16 = 0

now we will use quadratic formula: x = (-b (+/-) sq rt b^2 - 4ac) / (2a)

x^2 + 6x - 16 = 0
a = 1, b = 6, c = -16

now we sub into the quadratic formula..
x = (-6 (+/-) sq rt 6^2 - 4(1)(-16) / (2(1))
x = (-6 (+/-) sq rt 36 + 64) / 2
x = (-6 (+/-) sq rt 100) / 2
x = (-6 (+/-) 10) / 2

x = (-6 + 10) / 2
x = 4/2
x = 2

and
x = (-6 - 10)/2
x = -16/2
x = -8

so your solution is : x = 2 and x = -8

Answer 2

read this..it might help you..
http://www.purplemath.com/modules/quadform.htm