functions f(x)

[agille32]

Let f(x) =(x - 8)^2. Find x so that f(x)= 100

I believe this is saying to put (x-8)^2 = 100
I would then get the square root of (x-8)^2 and 100
?(x - 8)^2 = ?100
x-8 = 10
x=18

Is this correct?

 

[BigGlenntheHeavy]

\(\displaystyle No.\)

\(\displaystyle (x-8)^2 \ = \ 100\)

\(\displaystyle x-8 \ = \ \pm \ 10\)

\(\displaystyle x \ = \ 8 \ \pm \ 10\)

\(\displaystyle Hence, \ x \ = \ 18 \ or \ x \ = \ -2\)

\(\displaystyle I'll \ let \ you \ do \ the \ check.\)

 

[Deleted member 4993]

Let f(x) =(x - 8)^2. Find x so that f(x)= 100

I believe this is saying to put (x-8)^2 = 100
I would then get the square root of (x-8)^2 and 100
?(x - 8)^2 = ?100
x-8 = 10
x=18

Is this correct?

Another way:

\(\displaystyle (x \ \ - \ \ 8)^2\ \ = \ \ 10^2\)

\(\displaystyle (x \ \ - \ \ 8)^2\ \ - \ \ 10^2 \ \ = 0\)

\(\displaystyle (x \ \ - \ \ 8 \ \ + \ \ 10)\cdot (x \ \ - \ \ 8 \ \ - \ \ 10) \ \ = 0\)

\(\displaystyle (x \ \ + \ \ 2)\cdot (x \ \ - \ \ 18) \ \ = 0\)

so

x + 2 = 0 ? x = - 2

or

x - 18 = 0 ? x = 18

 

[agille32]

Thank you! :wink: