Yea so whats the question or is that just a fact<span />
I think the answer for your question is B
Our parent function is f(x)=x^2. A vertical stretch by a factor of k means that every point (x,f(x)), has been transformed into (x,kf(x)). Alex is clearly incorrect as our parent function has been transformed to (x,9f(x)), not (x,3f(x)). A horizontal stretch(or compression) by a factor of k means our function has been transformed to (x/k,f(x)). Here, Marta is saying our function should look like (3x,f(x)). This can also be achieved by plugging 3x into the parent function, which would give us f(3x)=(3x)^2, so it seems that Marta is the correct one.
(AB)^2 + (2 m)^2 = (8 m)^2, or
(AB)^2 + 4 m^2 = 64 m^2, or (AB)^2 = 60 m^2.
Taking the square root of both sides, (length of AB) = + 2sqrt(15) (answer)
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