Under a dilation, triangle A(0,0), B(0,4), C(6,0) becomes triangle A'(0,0), B'(0,10), C(15,0). What is the scale factor for this dilation?
What is a dilation?
What is a scale factor?
a dilation is a transformation (projection(?)) with a centre of enlargement. (With your problem this centre is the point A = A') The rate of length of corresponding lines is constant: That's the scale factor.