Final answer:
To factor the expression 4s²- 21s + 5 completely, the correct answer is option a) (4s - 5)(s - 1).
Step-by-step explanation:
To factor the expression 4s² - 21s + 5 completely, we need to find two binomials that, when multiplied, give us the original expression.
To do this, we can look for two numbers that multiply to give 20 (the product of the coefficient of s² and the constant term), and add up to -21 (the coefficient of s).
In this case, those numbers are -1 and -20.
Therefore, the factored form is (s - 1)(4s - 5), option a) (4s - 5)(s - 1).