Question

rút gọn    (y-3).(y+3).(y²+9)-(y²+2).(y²-2)

Answer 1

 

(y-3).(y+3).(y²+9)-(y²+2).(y²-2)

 =(y²-9)(y²+9)-(y⁴-4)

=y⁴-81-y⁴+4

=-77

Answer 2

\(\left(y-3\right)\left(y+3\right)\left(y^2+9\right)-\left(y^2-2\right)\left(y^2+2\right)=\left(y^2-9\right)\left(y^2+9\right)-\left(y^4-4\right)\)

\(=y^4-81-y^4+4=-81+4=-77\)