Step-by-step explanation:
the writing and spacing of the problem description is difficult to understand.
but there is no mystery. look at the examples.
all of them
3×5 = 15 = 16 - 1 = 4² - 1
4×6 = 24 = 25 - 1 = 5² - 1
5×7 = 35 = 36 - 1 = 6² - 1
6×8 = 48 = 49 - 1 = 7² - 1
7×9 = 63 = 64 - 1 = 8² - 1
8×10 = 80 = 81 - 1 = 9² - 1
so, what does this look like ?
(x-1)×(x+1) is always equal to (x² - 1)
