Razonamiento Matematico: octubre 2011

ECUACION #1
$\bg_white \fn_cs (x+7)(x-3)=x(x-3)+7(x-3)=x^{2}-3x+7x-21=x^{2}+4x-21$

ECUACION #2
$\bg_white \fn_cs (2x-5)(x+7)=2x(x+7)-5(x+7)=2x^{2}+14x-5x+35=2x^{2}+9x 35$

ECUACION #3
$\bg_white \fn_cs (x+2)(x-4)-x(x-2)=x(x-4)+2(x-4)-x(x-2)=x^{2}-4x+2x-8-x^{2}+2x=x^{2}-x^{2}-4x+2x+2x-8 =-8$

ECUACION #4
$\bg_white \fn_cs (2x-1)(4x^{2}+2x+1)=2x(4x^{2}+2x+1)-1(4x^{2}+2x+1)=8x^{3}+4x^{2}+2x-4x^{2}-2x-1=8x^{3}+4x^{2}-4x^{2}+2x-2x-1=8x^{3}-1$

ECUACION #5
$\bg_white \fn_cs (x-2y)(x^{2}+2xy+4y^{2})=x(x^{2}+2xy+4y^{2})-2y(x^{2}+2xy+4y^{2})=x^{3}+2x^{2}y+4xy^{2}-2x^{2}y-4xy^{2}-8y^{3}=x^{3}+2x^{2}y-2x^{2}y+4xy^{2}-4xy^{2}-8y^{3}=x^{3}-8y^{3}$

ECUACION #6
$\bg_white \fn_cs (x^{2}+3x+2)(x^{2}-3x+2)=x^{2}(x^{2}-3x+2)+3x(x^{2}-3x+2)+2(x^{2}-3x+2)=x^{4}-3x^{3}+2x^{2}+3x^{3}-9x^{2}+6x+2x^{2}-6x+4=x^{4}+3x^{3}-3x^{3}+2x^{2}+2x^{2}-9x^{2}+6x-6x+4=x^{4}-5x^{2}+4$