Question

Viết các biểu thức sau dưới dạng tổng: 

a.(a\(^2\)2+2a+3)(a\(^2\)2+2a-3)

b.(a\(^2\)2+2a+3)(a\(^2\)-2a-3)

c.(a\(^2\)2-2a+3)(a\(^2\)+2a-3)

Answer 1

\(a^22\) là a² nhân với 2 đó hả?

\(a,\left(a^22+2a+3\right)\left(a^22+2a-3\right)\)

\(=\left[\left(a^22+2a\right)+3\right]\left[\left(a^22+2a\right)-3\right]\)

\(=\left(a^22+2a\right)^2-9\)

\(=4a^4+8a^3+4a^2-9\)

\(b,\left(a^22+2a+3\right)\left(a^2-2a-3\right)\)

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

\(=2a^4-2a^3-7a^2-12a-9\)

\(c,\left(a^22-2a+3\right)\left(a^2+2a-3\right)\)

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

\(=2a^4+2a^3-7a^2+12a-9\)