Evaluate (using factors) : 301² x 300 - 300³

Use factor method to evaluate:

(5z² - 80) ÷ (z - 4)

Use factor method to evaluate:

10y(6y + 21) ÷ (2y + 7)

Use factor method to evaluate:

39x³(50x² - 98) ÷ 26x²(5x + 7)