Help me :( it's algebra and I am so confused. (explanation would be nice)

- 3 + 15x² - 3x

Step-by-step explanation:

Given

(5 - 3x + 8x²) - (8 - 7x²)

Remove the parenthesis on first and distribute second by - 1

= 5 - 3x + 8x² - 8 + 7x² ← collect like terms

= - 3 + 15x² - 3x ← in standard form

(n^3 - n)

= n(n-1)(n+1)

since it is divisible by 3 and 2 ,because it is a multiple 3 consecutive number

if, n-1 is odd then n+1 is also odd, then it is a multiple of 9

but if, n-1 is even then n+1 is also even, then it is a multiple of 4

so, largest multiple = max(9*2, 4*3) = max(18, 12) = 18