What is the quadratic formula for f(b)=b^2 - 4b + 4 = 0f(b)=b24b+4=0?

1 Answer
Oct 22, 2015

Rewriting f(b)f(b) as f(x)f(x) will permit you to use the standard formula with less confusion (since the standard quadratic formula uses bb as one of its constants)

Explanation:

(since the given equation uses bb as a variable, we will need to express the quadratic formula, which normally uses bb as a constant, with some variant, hatbˆb.

To help reduce confusion, I will rewrite the given f(b)f(b)as
color(white)("XX")f(x)=x^2-4x+4=0XXf(x)=x24x+4=0

For the general quadratic form:
color(white)("XX")hatax^2+hatbx+hatc=0XXˆax2+ˆbx+ˆc=0
the solution given by the quadratic equation is
color(white)("XX")x=(-hatb+-sqrt(hatb^2-4hatahatc))/(2hata)XXx=ˆb±ˆb24ˆaˆc2ˆa

With hata = 1ˆa=1, hatb=-4ˆb=4, and hatc=+4ˆc=+4
we get
color(white)("XX")b=(x=)(4+-sqrt((-4)^2+4(1)(4)))/(2(1))XXb=(x=)4±(4)2+4(1)(4)2(1)
as the quadratic formula