Răspuns :
a) (x+3)²+(x+1)²-(2x+1)(2x-1)=
= x²+6x+9 + x²+2x+1 -(4x²-1)=2x²+8x+10 - 4x²+1 = -4x²+8x+11 ;
b) (2x+5)²-(3x-5)²+(2x+7)(2x-7)=
= 4x²+20x+25 - (9x²-30x+25) + 4x²-49 =
= 4x²+20x+25 - 9x²+30x-25 + 4x²-49 = - x² +50x - 49 ;
= x²+6x+9 + x²+2x+1 -(4x²-1)=2x²+8x+10 - 4x²+1 = -4x²+8x+11 ;
b) (2x+5)²-(3x-5)²+(2x+7)(2x-7)=
= 4x²+20x+25 - (9x²-30x+25) + 4x²-49 =
= 4x²+20x+25 - 9x²+30x-25 + 4x²-49 = - x² +50x - 49 ;