1,9(2a+3b)^2-4(3a-2b)^2 2,已知x+3y=0,求x^3+3x^2y-2x-6y的值

1,9(2a+3b)^2-4(3a-2b)^2 2,已知x+3y=0,求x^3+3x^2y-2x-6y的值
1,9(2a+3b)^2-4(3a-2b)^2 2,已知x+3y=0,求x^3+3x^2y-2x-6y的值

1,9(2a+3b)^2-4(3a-2b)^2 2,已知x+3y=0,求x^3+3x^2y-2x-6y的值
1,9(2a+3b)^2-4(3a-2b)^2
=(6a+9b)²-(6a-4b)²
=(6a+9b+6a-4b)(6a+9b-6a+4b)
=(12a+5b)*13b
=13b(12a+5b)
2,已知x+3y=0,求x^3+3x^2y-2x-6y的值
x^3+3x^2y-2x-6y
=x²(x+3y)-2(x+3y)
=(x²-2)(x+3y)
=(x²-2)*0
=0

1.
9(2a+3b)^2-4(3a-2b)^2
=[3*(2a+3b)]^2-[2*(3a-2b)]^2
=(6a+9b)^2-(6a-4b)^2
=[(6a+9b)+(6a-4b)]*[(6a+9b)-(6a-4b)]
=(12a+5b)*13b
=13b(12a+5b)
2.
x^3+3x^2y-2x-6y
=(x+3y)(x^2-2)
=0*(x^2-2)
=0
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