Question

Which of the following is a factor of 5x3 + 320?

Answer 1

Multiply 5 by 3, then add that result to 320.
If you like, use your calculator for the next step:
Divide your new number (let's call it n) by the numbers you have to choose from. If n is perfectly divisible by one of the numbers, that is the number that is a factor of n.

For example, if you have the number 20, and you have to chose whether 3 or 4 is a factor, divide by one first, say 3, and see what your answer is. Is your answer an integer?
If you divide 20 by 3, you get 6.6666 repeating, which is not an integer (integers are whole numbers, like 1, 2, 3, 4, 5, etc)
If you divide 20 by 4, you get 5, which is a whole number, therefore 4 is a factor of 20.

Try this method with your question and see if it works.

Answer 2

is the problem 5x^3 + 320 ? or is it just 5 * 3 + 320 ?

Answer 3

5x^3 + 320 =5(X^3+64) factorize (X^3+64) and u will get the required ans