Question

Consider the polynomial function g(x) = 8x5 + ax4 + 5x + 20, where a is an unknown real number. If (x+4) is a factor of g(x), what is the value of a?

Answer 1

`g(x) =8x^5 + ax^4 +5x +20 \\\\\text{If}~ x +4 ~ \text{is a factor of g(x) then,}~ \\\\g(-4)=0\\\\\implies 8(-4)^5 +a(-4)^4+5(-4) +20 = 0\\\\\implies 256a -8192 = 0\\\\\implies a = (8192)/(256) = 32`