用因式分解的平方差解下列各式!1.12x²-272.(x-2y)²-43.(x+1)²-（2x-3）²4.m²-9n²-m-3n

Question

用因式分解的平方差解下列各式!
1.12x²-27
2.(x-2y)²-4
3.(x+1)²-（2x-3）²
4.m²-9n²-m-3n

Answer 1

1.12x²-27
=（2√3x+3√3）(2√3x-3√3)
2.(x-2y)²-4
=(x-2y+2)(x-2y-2);
3.(x+1)²-（2x-3）²
=(x+1+2x-3)(x+1-2x+3)
=(3x-2)(4-x);
4.m²-9n²-m-3n
=(m+3n)(m-3n)-(m+3n)
=(m+3n)(m-3n-1);
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