Question

A polynomial $y = ax^3 + bx^2 + cx + d$ intersects x-axis at 1 and -1, and y-axis at 2. The value of b is:

Accepted Answer

A. At $(0, 2) \implies d = 2$. At $(1, 0) \implies a + b + c + 2 = 0$. At $(-1, 0) \implies -a + b - c + 2 = 0$. Adding the two equations: $2b + 4 = 0 \implies b = -2$.

Cubic Polynomial Coefficient

Explanation

Practise this under exam conditions