Could you help with these please

Determine the point(s) at which the graph of the following function as a horizontal tangent. x2 41; 24.) f(x) = 23.) f(x) = 4 x1 +4 2 I Find an equation of the tangent line to the graph off at the indicated point and then use your calculator to conrm the results. 22.) f(x)=(x2)(x13x1) at (1,9)