解
(2b+3a)(3a-2b)
=(3a)²-(2b)²
=9a²-4b²
(x+y-z)(x-y-z)
=[(x-z)+y][(x-z)-y]
=(x-z)²-y²
=x²-2zx+z²-y²
(3x-2)(2-3x)
=-(3x-2)²
=-(9x²-12x+4)
=-9x²+12x-4
解
(2b+3a)(3a-2b)
=(3a)²-(2b)²
=9a²-4b²
(x+y-z)(x-y-z)
=[(x-z)+y][(x-z)-y]
=(x-z)²-y²
=x²-2zx+z²-y²
(3x-2)(2-3x)
=-(3x-2)²
=-(9x²-12x+4)
=-9x²+12x-4