Câu hỏi của ID Mini World: 71156040

Question

Áp dụng hằng đẳng thức

Yen Nhi · Accepted Answer

a) $\left(a^2-1\right)^3-\left(a^4+a^2+1\right)\left(a^2-1\right)$

$=a^6-3a^4+3a^2-1-a^6+1$

$=-3a^4+3a^2$

b) $\left(a^4-3a^2+9\right)\left(a^2+3\right)-\left(3+a^2\right)^3$

$=a^6+27-27-27a^2-9a^4-a^6$

$=-9a^4-27a^2$

Câu trả lời:

a) $\left(a^2-1\right)^3-\left(a^4+a^2+1\right)\left(a^2-1\right)$

$=a^6-3a^4+3a^2-1-a^6+1$

$=-3a^4+3a^2$

b) $\left(a^4-3a^2+9\right)\left(a^2+3\right)-\left(3+a^2\right)^3$

$=a^6+27-27-27a^2-9a^4-a^6$

$=-9a^4-27a^2$