Answer:
1) (x+1)(x-1)
= x²+x-x-1
= x²-1 ans...
2) (y-2)(y+2)
= y²-2y + 2y - 4
= y²- 4 ans...
3) (x+4)(x-4)
= x² +4x - 4x - 16
= x² - 16 ans...
4) (2y+5)(2y-5)
= 4y² + 10y -10 y - 25
= 4y² - 25 ans...
5) (2x+4)(2x-4)
= 4x² + 8x - 8x - 16
= 4x² - 16 ans...
