[tex]1) \\ (2 x^{2} +x+2)+(2x+3)=2 x^{2} +3x+5 \\(2 x^{2} +x+2)-(2x+3)=2 x^{2} -x-1 \\ (2 x^{2} +x+2)(2x+3)=4x^3+8 x^{2} +7x+6 \\ 2) \\ \frac{16x^3}{4x+x+3x}= \frac{16x^3}{8x}=2 x^{2} \\ 3) \\ (x-a)(x+a)= x^{2} -25; x^{2} -a^2= x^{2} -25 \\ a^2=25;a=-5;sau :a=5 \\ 5) \\ a^2-b^2=(a+b)(a-b)=21 \\ 7(a-b)=21 \\ a-b=3 [/tex]
[tex]4)E(2)=(2-3)^2+(4-2)=1+2=3[/tex]
