a: \(\left(a^2+2a+3\right)\left(a^2-2a-3\right)\)

\(=\left[a^2+\left(2a+3\right)\right]\left[a^2-\left(2a+3\right)\right]\)

\(=\left(a^2\right)^2-\left(2a+3\right)^2\)

\(=a^4-\left(2a+3\right)^2\)

b: \(\left(-a^2-2a+3\right)^2\)

\(=\left(a^2+2a-3\right)^2\)

\(=a^4+4a^2+9+4a^3-18a-6a^2\)

\(=a^4+4a^3-2a^2-18a+9\)

c: \(\left(x-y-z\right)^2\)

\(=x^2-2x\left(y+z\right)+\left(y+z\right)^2\)

\(=x^2-2xy-2xz+y^2+2yz+z^2\)

d: \(\left(x+y+z\right)\left(x-y-z\right)\)

\(=x^2-\left(y+z\right)^2\)

\(=x^2-y^2-2yz-z^2\)

Program hotrotinhoc;

var n,x,i: integer;

s: real;

function t1(d: integer): longint;

var i,t: longint;

begin

t:=1;

for i:=1 to d do t:=t*i;

t1:=t;

end;

function t2(a,b: integer): longint;

var i,tg: integer;

begin

tg:=1;

for i:=1 to a do tg:=tg*b;

t2:=tg;

end;

begin

write('n='); readln(n);

write('x='); readln(x);

s:=1;

for i:=1 to n do

if i mod 2=1 then s:=s-((t2(i,x))/(t1(i))) else s:=s+((t2(i,x))/(t1(i)));

write(s:1:2);

readln

end.

(9+x)(x-3)

1. 

2.

 \(\begin{array}{l}\left( {3x - 2y} \right)\left( {9{x^2} + 6xy + 4{y^2}} \right) + 8{y^3}\\ = \left( {3x - 2y} \right)\left[ {{{\left( {3x} \right)}^2} + 3x.2y + {{\left( {2y} \right)}^2}} \right] + 8{y^3}\\ = {\left( {3x} \right)^3} - {\left( {2y} \right)^3} + 8{y^3}\\ = 27{x^3} - 8{y^3} + 8{y^3}\\ = 27{x^3}\end{array}\)

( \(\sqrt{x}+3\) )/ ( x + x*\(\sqrt{x}\) )

(sqrt(x)+3)/(x+x*sqrt(x))

Tích của 3 và x là : 3x

Tổng của 5 và y : 5 + y

\(\dfrac{9}{4}\)