Transforming Functions
Questions involving reflecting or shifting graphs stump a great many students. But this needn’t be! Four simple rules govern all transformation questions encountered on the SAT/ACT. Master these laws, and all such questions suddenly become easy ones. Listed below is what you need to know. - Horizontal Reflection (across the y-axis) Replace x with -x. For example: If f(x) = x^2– x+1, the horizontal reflection is f(x) = (-x)^2–(-x)+1 = x^2+x+1. Vertical Reflection (across the x-axis) Replace y with -y. For example: If g(x) = 3x–2 i.e. y = 3x–2, the vertical reflection is (-y) = 3x–2 and y = -3x+2. Therefore, g(x) = -3x+2. Horizontal Shift, h units Replace x with x–h. For example: If f(x) = x^2–x is shifted 4 units left, h = -4, h–k = h–(-4) = h+4, and the shifted function is f(x) = (x+4)^2–(x+4) = x^2+8x+16–x–4 = x^2+7x+12. Vertical Shift, k units Replace y with y-k (or simply add k to the function). For example: If y = |6x–1| is shifted 3 units up, k = 3, y–k = y–3, and the s...