pls explaing by tep by step

Answer:
a = 3
Step-by-step explanation:
If (x+3) is a factor of f(x) = x³+ax²+x+3,
From remainder theorem,
When we substitute -3 into the expression, we equate to zero
That is,
F(-3) = 0
(-3)³+a(-3)²+(-3)+3 = 0
-27+9a-3+3 = 0
9a = 27
divide both sides by the coefficient of a
a = 27/9
a = 3
Hence the value of a = 3