Question

Arătați ca (2x+1)²-2(x-1)²+(1x)(x+3)=(x+3)²-7 ori ce ar fi x nr real!?

Answer 1

$( 2x)^{2} +2*2x*1+ 1^{2} -2*( x^{2} -2x*1+ 1^{2} )+x*x+3x$=$x^{2} +2x*3+ 3^{2} -7$
[tex]4x^{2} +4x+1-2*( x^{2} -2x+1)+ x^{2} +3x= x^{2} +6x+9-7 [/tex]
[tex] 4x^{2} +4x+1- 2x^{2} +4x-2+ x^{2} +3x= x^{2} +6x+2 [/tex]
$(4-2+1-1) x^{2} +(4+4+3-6)x+1-2-2= 2x^{2} +5x-3$