Question

x-y=1 thì x\(^3\)-y\(^3\)-3xy bằng bao nhiêu

Answer 1

\(x^3-y^3-3xy\)

\(=x^3-y^3-3xy\left(x-y\right)\)

\(=\left(x-y\right)^3=1\)

Answer 2

Theo giả thiết:

\(x-y=1\Rightarrow x-1=y\Rightarrow\left(x-1\right)^3=y^3\Rightarrow x^3-3x^2+3x-1=y^3\Rightarrow x^3-y^3-3xy=3x^2-3x+1-3xy\)

\(\Rightarrow x^3-y^3-3xy=3x\left(x-1-y\right)+1=3x\left[\left(x-y\right)-1\right]+1=0+1=1\)

Answer 3

x-y=1=> (x-y)³=1

<=> x³- 3x³y - 3xy³ - y³

<=>x³ - y³ - 3xy(x+y)

=> x³-y³-3xy = 1

 

 

Answer 4

x^3_y^3_3xy=1