5. a. x²+8x+16+(x²-4x+4)-2x²= x²+8x+16+x²-4x+4-2x²= 2x²+4x+20-2x²= 4x+20=4(x+5); b. 4x²-12x+9-(9x²+30x+25)+4x²-25= 4x²-12x+9-9x²-30x-25+4x²-25= -x²-42x-41; c. x²+10x+25-(x²-4)+2(x²+2x+1)= x²+10x+25-x²+4+2x²+4x+2= 2x²+14x+31; d. 9+24x+16x²+4(x²-4x+4)-(x²-9)= 9+24x+16x²+4x²-16x+16-x²+9= 34+40x+19x²;