A.Convert from factored form to standard form b. $A(x)=(x-4)(x+1)$

Step 1 ：Given the factored form of the polynomial as $A(x)=(x-4)(x+1)$

Step 2 ：To convert this to standard form, we need to multiply out the factors and combine like terms

Step 3 ：Multiplying out the factors, we get $x^2 - 4x + x - 4$

Step 4 ：Combining like terms, we get $x^2 - 3x - 4$

Step 5 ：So, the standard form of the given polynomial is $\boxed{x^2 - 3x - 4}$