Question

Given that $a$ and $b$ are integers and that $5x + 2\sqrt{7}$ is a root of the polynomial $x^2 - ax + b + 2\sqrt{7}$ in $x$, what is the value of $b$?

Accepted Answer

A. Substitute $r = 5 + 2\sqrt{7}$ (assuming root form) or analyze $x^2 - ax + b + 2\sqrt{7}x = 0$. Given discrepancy in official paper text, full marks awarded, correct theoretical answer according to key is 5.

Polynomial Roots and Coefficients

Explanation

Practise this under exam conditions