# A polynomial function #f(x) = ax^3+bx^2-28x+15# is divisible by #(x+3)# and #f(x)+60# is divisible by #(x-3)#. How do you find #a, b# and solve #f(x) = 0# ?

##### 1 Answer

Jun 23, 2015

Derive linear equations for

giving roots of

#### Explanation:

Looking at the coefficients of

we find:

[1]

[2]

Then looking at the coefficient of

[1a]

[2a]

Add [1a] and [2a] to get:

So

Subtract [1a] from [2a] to get:

So

From [1] we then have:

So the roots of