Question

rezolvați folosind formula (a±b)³=a³±b³±3ab(a±b)³

a) (x-1)³=
b) (2x+1)³=
​

Answer 1

Răspuns:

$a) {(x - 1)}^{3} = {x}^{3} - 3 {x}^{2} \times 1 - 3 \times x \times {1}^{2} + {1}^{3} = \\ = {x}^{3} - 3 {x}^{2} - 3x + 1$

$b) {(2x + 1)}^{3} = (2x) ^{3} + 3 \times ( {2x})^{2} \times 1 + 3 \times 2x \times {1}^{3} + {1}^{3} = \\ = 8 {x}^{3} + 3 \times 4 {x}^{2} + 6x + 1 = \\ = {8x}^{3} + 12 {x}^{2} + 6x + 1$