Question

Khai triển các phép tính sau

A, (a - b ) × ( a - b )

B, ( a + b ) × ( a -b )

C, ( a + b ) ( a^2 - ab + b^2 )

Answer 1

\(\left(a-b\right)\left(a-b\right)\)

\(=a\left(a-b\right)-b\left(a-b\right)\)

\(=a^2-ab-ab+b^2\)

\(=a^2-2ab+b^2\)

\(\left(a+b\right)\left(a-b\right)\)

\(=a\left(a-b\right)+b\left(a-b\right)\)

\(=a^2-ab+ab-b^2\)

\(=a^2-b^2\)

\(\left(a+b\right)\left(a^2-ab+b^2\right)\)

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

\(=\left(a+b\right)\left(a-b\right)\left(a-b\right)\)

\(=\left(a^2-b^2\right)\left(a-b\right)\)

\(=a^2\left(a-b\right)-b^2\left(a-b\right)\)

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

p/s thật ra cái này áp dụng hđt là ra ồi