①(2x+3)²-(2x-3)²
=[(2x+3)+(2x-3)]*[(2x+3)-(2x-3)]
=4x*6
=24x
②(a+b-2c)(-a+b+2c)
=[b+(a-2c)]*[b-(a-2c)]
=b²-(a-2c)²
=b²-(a²-4ac+4c²)
=b²- a²+4ac-4c²
①(2x+3)²-(2x-3)²
=[(2x+3)+(2x-3)]*[(2x+3)-(2x-3)]
=4x*6
=24x
②(a+b-2c)(-a+b+2c)
=[b+(a-2c)]*[b-(a-2c)]
=b²-(a-2c)²
=b²-(a²-4ac+4c²)
=b²- a²+4ac-4c²