Asked by dan

I was wondering if my answer is right.
Let f (x)=(x+10)^2. Find x so that f(x)=72

(x+10)^2=72
x^2+20x+100=72
x^2+20x+28=0
x=(-20+-sqrt(400-112))/2
x=-10+6*sqrt(2)
Answered by Mike
Yeap! Your answer looks good. Don't forget that the sign before your radical can be +/-, thus yielding two answers!
-10+6*sqrt(2) AND -10-6*sqrt(2)
Answered by dan
Thank you for your help and reminding me there is two answers.
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