Select the correct answer. What is the completely factored form of this polynomial? 5x4 + 20x3 − 105x2 A. 5x3(x + 3)(x − 7) B. 5x2(x − 3)(x + 7) C. 5x3(x − 3)(x + 7) D. 5x2(x + 3)(x − 7)

B.5: 5^2(-3)(+7)

Step-by-step explanation:

1. 5 is the HCF of the three numbers, so it goes outside the brackets. 5(^4+4^3−21^2).

2. ^2 is also a factor, so now its 5^2(^2+4-21)

3. Factor by Grouping 5^2(^2−3+7−21)

4. Factor by Grouping 5^2((−3)+7(−3))

5. Factor by Grouping 5^2(−3)(+7)

Thats your final answer.