Factor the polynomial , show how you got answers

147x² - 84x + 12
3(49x²) - 3(28x) + 3(4)
3(49x² - 28x + 4)
3(49x² - 14x - 14x + 4)
3(7x(7x) - 7x(2) - 2(7x) - 2(-2))
3(7x(7x - 2) - 2(7x - 2))
3(7x - 2)(7x - 2)
3(7x - 2)²

(x - 10)² - 36
((x - 10)(x - 10)) - 36
(x(x - 10) - 10(x - 10)) - 36
(x(x) - x(10) - 10(x) + 10(10)) - 36
(x² - 10x - 10x + 100) - 36
(x² - 20x + 100) - 36
x² - 20x + 100 - 36
x² - 20x + 64
x² - 16x - 4x + 64
x(x) - x(16) - 4(x) - 4(-16)
x(x - 16) - 4(x - 16)
(x - 4)(x - 16)

21y³ - 6y² + 15y
3y(7y²) - 3y(2y) + 3y(5)
3y(7y² - 2y + 5)