Help with factoring? are these right?

Question

factor: 16x^2-81
is it 8(2x^2-9) ?

and: 3-12y
is it 3(-4y)??

help with thia? 2x^2+7x= ?

thanks!

Answer 1

16x² - 81 = (4x)² - 9² = (4x-9)(4x+9)

3-12y = 3(1 - 4y)

2x²+7x = x(2x+7)

.,.,.,.,

Answer 2

1) Simplifying
16x2 + -81

Reorder the terms:
-81 + 16x2

Factor a difference between two squares.
(9 + 4x)(-9 + 4x)

Final result:
(9 + 4x)(-9 + 4x)



2) Simplifying
3 + -12y

Factor out the Greatest Common Factor (GCF), '3'.
3(1 + -4y)

Final result:
3(1 + -4y)




3) Simplifying
2x^2 + 7x

Reorder the terms:
7x + 2x^2

Factor out the Greatest Common Factor (GCF), 'x'.
x(7 + 2x)

Final result:
x(7 + 2x)

Answer 3

Question 1
16 x ² - 81
( 4 x - 9 ) ( 4 x + 9 )

Question 2
3 - 12y
3 (1 - 4 y )

Question 3
2 x ² + 7 x
x ( 2 x + 7)

Answer 4

16x^2 - 81
(4x - 9)(4x + 9)

3 - 12y
3(1-4y)

2x^2 + 7x
x(2x + 7)