[difference of squares][section 42]

(1.) x² - 25 here is the problem

= (x - 5)(x + 5) factor

(2.) y² - 36 here is the problem

= (y - 6)(y + 6) factor

(3.) 9x² - 4 here is the problem

= (3x - 2)(3x + 2) factor

(4.) 16y² - 36 here is the problem

= 4(4y² - 9) factor

= 4(2y - 3)(2y + 3) factor

(5.) 1 - 81y² here is the problem

= (1 - 9y)(1 + 9y) factor

(6.) y⁶ - 100 here is the problem

= (y³ - 10)(y³ + 10) factor

(7.) x² + y² here is the problem

[not factorable]

(8.) 25x² - 49 here is the problem

= (5x - 7)(5x + 7) factor

(9.) x² - y⁴ here is the problem

= (x - y²)(x + y²) factor

(10.) x²y² - z² here is the problem

= (xy - z)(xy + z) factor