phân tích đa thức thành nhân tử: $0,125\left(a+1\right)^3-1$

ô mai gót

$0,125\left(a+1\right)^3-1$

$=\left\lbrack0,5.\left(a+1\right)^3\right\rbrack-1^3$

$=\left(0,5a+0,5\right)^3-1^3$

$=\left(0,5a+0,5-1\right)\left\lbrack\left(0,5a+0,5\right)^2+\left(0,5a+0,5\right).1+1^2\right\rbrack$

$=\left(0,5a-\frac{1}{2}\right)\left(0,25a^2+0,5a+0,25+0,5a+0,5+1\right)$

$=\left(0,5a-\frac{1}{2}\right)\left(0,25a^2+a+1,75\right)$

$=0,5\left(a-1\right).0,25\left(a^2+4a+7\right)$

$=0,125\left(a-1\right)\left(a^2+4a+7\right)$.