Expression 3: "r" equals negative 4 StartFraction, left parenthesis, "a" minus "x" , right parenthesis left parenthesis, "b" minus "x" , right parenthesis Over left parenthesis, "a" minus "b" , right parenthesis squared , EndFraction Has graph. To audio trace, press ALT+T.r=−4a−xb−xa−b2