(Unknown remainder – quadratic divisor)
Let f(x) be a polynomial of degree 4 which, on division by g(x)=x2+3x−1, leaves quotient q(x)=x2−2x+4 and remainder r(x)=ax+b, where a and b are real numbers. Further, it is given that f(1)=10 and f(−3)=20.
(i) Express f(x) in terms of a and b.
(ii) Using the given values of f(1) and f(−3), obtain two equations in a and b and hence determine their values.
(iii) Write the complete expression for f(x) and find the value of f(−1).