The expression x2 - 2x - 15x2 + 8x + 15 × (x2 + 4x - 5) is equal to:

Solve this: (12)2 - (4.5)2(12)2 + 12 × 4.5 + (4.5)2

If x = 4, what is the value of 2x + 3?

If A ⇌ B = A3 + B3 - 3AB, then find the value of 2 ⇌ 1.