Question

莎

求過程...

(2) (a − 2b)² – 6(4b²-a²) + 9(a + 2b)² =

Answer 1

曾幾何時

令a-2b=A，a+2b=B

4b^2-a^2=(a+2b)(a-2b)=AB

題目=A^2-6AB+9B^2=(A-3B)^2=(-2a-8b)^2