Răspuns:
9·(x²-x+1)
Explicație pas cu pas:
(x+1)³-(x-2)³ = ?
Notam :
x+1 = a ; x-2 = b
Folosim formula :
a³-b³ = (a-b)(a²+ab+b²)
Inlocuim in formula :
(x+1)³-(x-2)³ = (x+1-x+2)[(x+1)²+(x+1)(x-2)+(x-2)²] =
= 3·(x²+2x+1+x²-x-2+x²-4x+4) = 3·(3x²-3x+3) = 9·(x²-x+1)
(x+1)³-(x-2)³ = 9·(x²-x+1)
