8(m-n)^2-18(m-2n)^2

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8(m-n)^2-18(m-2n)^28(m-n)^2-18(m-2n)^28(m-n)^2-18(m-2n)^2原式=2[4(m-n)^2-9(m-2n)^2]=2[(2m-2n)^2-(3m-6n

8(m-n)^2-18(m-2n)^2
8(m-n)^2-18(m-2n)^2

8(m-n)^2-18(m-2n)^2
原式=2[4(m-n)^2-9(m-2n)^2]
=2[(2m-2n)^2-(3m-6n)^2]
=2(2m-2n-3m+6n)(2m-2n+3m-6n)
=2(-m+4n)(5m-8n)
=-2(m-4n)(5m-8n)

8(m-n)^2-18(m-2n)^2
=2[4(m-n)²-9(m-2n)²]
=2[2(m-n)+3(m-2n)][2(m-n)-3(m-2n)]
=2(5m-8n)(4n-m)

是要求因式分解吗?
8(m-n)^2-18(m-2n)^2
=2((2(m-n))²-(3(m-2n))²)
=2(2m-2n+3m-6n)(2m-2n-3m+6n)
=2(5m-8n)(-m+4n)
=-2(5m-8n)(m-4n)

原式=8(m²-2mn+n²)-18(m²-4mn+4n²)
=8m²-16mn+8n²-18m²+72mn+72n²=-10m²+56mn-64n²
=-2(5m-8)(m-4)

=8(m^2-2mn+n^2)-18(m^2-4mn+4n^2)
=-10m^2+56mn^2-64n^2