How do you factor the difference of two cubes \[{{x}^{3}}-216?\]
Answer
617.1k+ views
Hint: As here we have to factor the difference of two cubes. You can use the formula for factoring the given equation \[{{x}^{3}}-216\] is \[{{a}^{3}}-{{b}^{3}}=(a-b)\left( {{a}^{2}}+ab+{{b}^{2}} \right).\]
Here compare the given equation \[{{x}^{3}}-216\] by \[{{a}^{3}}-{{b}^{3}}\] and identify the value of \[a\]and \[b.\]
Complete step by step solution:
As we know that, we have to factor the difference of two cubes \[{{x}^{3}}-216.\]
The formula for factoring difference of \[2\]cubes is \[{{a}^{3}}-{{b}^{3}}=(a-b)({{a}^{2}}+ab+{{b}^{2}}).\]
The given equation is\[,\]
\[\Rightarrow \]\[{{x}^{3}}-216\]
Here, compare the given equation with \[{{a}^{3}}-{{b}^{3}}\]
Therefore,
\[\Rightarrow \]\[{{a}^{3}}={{x}^{3}}\]and
\[\Rightarrow \]\[{{b}^{3}}=216\]
\[\Rightarrow \]\[{{a}^{3}}={{x}^{3}}\]
Transfer cube of left side to right side and here cube will be converted into cube root.
Therefore,
\[\Rightarrow \]\[a=\sqrt[3]{{{x}^{3}}}\]
Above cube root and cube will get cancel,
\[\therefore a=x\]
and
\[\Rightarrow {{b}^{3}}=216\]
Transfer the cube from left side to right side and it will get converted into a cube root.
Therefore,
\[\Rightarrow \]\[b=\sqrt[3]{216}\]
\[\Rightarrow \]\[b=6\]
Substitute the value of \[a=r,b=6\] into the formula of \[\left( a-b \right)\left( {{a}^{2}}+ab+{{b}^{2}} \right).\]
Therefore the equation will be,
\[\Rightarrow \]\[\left( x-6 \right)\left( {{x}^{2}}+x\times 6+{{6}^{2}} \right)\]
\[\Rightarrow \]\[\left( x-6 \right)\left( {{x}^{2}}+6x+36 \right)\]
Hence \[\left( x-6 \right)\left( {{x}^{2}}+6x+36 \right)\] is the factored form of \[{{x}^{3}}-216.\]
Note: Here remember that you have of to use the formula of
\[{{a}^{3}}-{{b}^{3}}=\left( a-b \right)\left( {{a}^{2}}+ab+{{b}^{2}} \right)\]
And choose \['a'\] and \['b'\] term from the given equation.
Apply the formula of difference of two cubes and in this way you will get the factored form of the given equation.
Here compare the given equation \[{{x}^{3}}-216\] by \[{{a}^{3}}-{{b}^{3}}\] and identify the value of \[a\]and \[b.\]
Complete step by step solution:
As we know that, we have to factor the difference of two cubes \[{{x}^{3}}-216.\]
The formula for factoring difference of \[2\]cubes is \[{{a}^{3}}-{{b}^{3}}=(a-b)({{a}^{2}}+ab+{{b}^{2}}).\]
The given equation is\[,\]
\[\Rightarrow \]\[{{x}^{3}}-216\]
Here, compare the given equation with \[{{a}^{3}}-{{b}^{3}}\]
Therefore,
\[\Rightarrow \]\[{{a}^{3}}={{x}^{3}}\]and
\[\Rightarrow \]\[{{b}^{3}}=216\]
\[\Rightarrow \]\[{{a}^{3}}={{x}^{3}}\]
Transfer cube of left side to right side and here cube will be converted into cube root.
Therefore,
\[\Rightarrow \]\[a=\sqrt[3]{{{x}^{3}}}\]
Above cube root and cube will get cancel,
\[\therefore a=x\]
and
\[\Rightarrow {{b}^{3}}=216\]
Transfer the cube from left side to right side and it will get converted into a cube root.
Therefore,
\[\Rightarrow \]\[b=\sqrt[3]{216}\]
\[\Rightarrow \]\[b=6\]
Substitute the value of \[a=r,b=6\] into the formula of \[\left( a-b \right)\left( {{a}^{2}}+ab+{{b}^{2}} \right).\]
Therefore the equation will be,
\[\Rightarrow \]\[\left( x-6 \right)\left( {{x}^{2}}+x\times 6+{{6}^{2}} \right)\]
\[\Rightarrow \]\[\left( x-6 \right)\left( {{x}^{2}}+6x+36 \right)\]
Hence \[\left( x-6 \right)\left( {{x}^{2}}+6x+36 \right)\] is the factored form of \[{{x}^{3}}-216.\]
Note: Here remember that you have of to use the formula of
\[{{a}^{3}}-{{b}^{3}}=\left( a-b \right)\left( {{a}^{2}}+ab+{{b}^{2}} \right)\]
And choose \['a'\] and \['b'\] term from the given equation.
Apply the formula of difference of two cubes and in this way you will get the factored form of the given equation.
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