Yvaries directly with x, and y = 5 when x = 4. what is the value of x when y = 8

Consider the function f left parenthesis x right parenthesis equals 4 x squared minus 3 x minus 1f(x)=4x2−3x−1 and complete parts (a) through (c). (a) find f left parenthesis a plus h right parenthesis f(a+h); (b) find startfraction f left parenthesis a plus h right parenthesis minus f left parenthesis a right parenthesis over h endfraction f(a+h)−f(a) h; (c) find the instantaneous rate of change of f when aequals=77.