[tex]a)\ \ (x-2)(x+2)=x^2+2x-2x-4=x^2-4\\\\b)\ \ (x-9)(x+9)=x^2+9x-9x-81=x^2-81\\\\c)\ \ (2x-1)(2x+1)=2x\cdot2x+2x\cdot1-1\cdot2x-1=4x^2+2x-2x-1=4x^2-1\\\\d)\ \ (6+4x)(4x-6)=24x-36+16x^2-24x=-36+16x^2=16x^2-36\\\\e)\ \ (3x-8y)(3x+8y)=3x\cdot3x+3x\cdot8y-8y\cdot3x-8y\cdot8y=9x^2+24xy-24xy-64y^2=\\\\=9x^2-64y^2\\\\f)\ \ (x+y)(y-x)=xy-x^2+y^2-xy=-x^2+y^2[/tex]
lub można zastosować wzór skróconego mnożenia
[tex](a-b)(a+b)=a^2-b^2[/tex]
[tex]a)\ \ (x-2)(x+2)=x^2-2^2=x^2-4\\\\b)\ \ (x-9)(x+9)=x^2-9^2=x^2-81\\\\c)\ \ (2x-1)(2x+1)=(2x)^2-1^2=4x^2-1\\\\d)\ \ (6+4x)(4x-6)=(4x+6)(4x-6)=(4x)^2-6^2=16x^2-36\\\\e)\ \ (3x-8y)(3x+8y)=(3x)^2-(8y)^2=9x^2-64y^2\\\\f)\ \ (x+y)(y-x)=(y+x)(y-x)=y^2-x^2[/tex]
