Question

Which equations are true?

Select all that apply.
9x² − 1 = (3x − 1)(3x + 1)
25x² 12 = (5x −6)(5x + 6)
16x² - 18y² = (8x − 9y) (8x +9y)
16x² - 64y² = (4x − 8y) (4x + 8y)
x² - 169 = (x − 13)(x + 13)

Answer 1

Hi :)

To answer this, you’ll only need to verify the following formula:
a^2 - b^2 = (a-b) (a+b)

Let’s try with the first one.
a^2 - b^2

—> The second one is not. 6 is not the square root of 12.
—-> The third one is false as well.
——> The fourth one is true. a^2 - b^2 = 16x^2 - 64y^2
a = 4x
b = 8y
So (a - b) (a + b) = (4x - 8y) (4x + 8y)
——-> The last one us true. a^2 - b^2 = x^2 - 169
a = x
b = 13
So (a - b) (a + b) = (x - 13) (x + 13)


I hope this helped! Have a nice day :)