How do you factor $4{x^3} + 32$?
Answer
623.7k+ views
Hint: First step is to take out the common factor of 4.
Then use the sum of cubes formula.
And factorize generally to achieve the solution.
Complete Step by Step Solution:
Let us start by writing the given equation:
$ \Rightarrow 4{x^3} + 32$
We will take out the common factor 4 out of $4{x^3}$ we get:
$ \Rightarrow 4\left( {{x^3}} \right) + 32$
Again take out the common factor 4 out of 32 we get:
$ \Rightarrow 4\left( {{x^3}} \right) + 4\left( 8 \right)$
Now, take out the common factor 4 out of the whole above equation we get:
$ \Rightarrow 4\left( {{x^3} + 8} \right)$
Rewrite 8 as ${2^3}$ we get:
$ \Rightarrow 4\left( {{x^3} + {2^3}} \right)$ ……. Let it be eq. $\left( 1 \right)$
Since, both terms are perfect cubes, factor using the sum of cubes formula:
$ \Rightarrow \left( {{a^3} + {b^3}} \right) = \left( {a + b} \right)\left( {{a^2} - ab + {b^2}} \right)$
Where, the values of the variables are as: $a = x$ and $b = 2$
Now substitute the values of a and b in the sum of cubes formula we will get:
$ \Rightarrow \left( {{x^3} + {2^3}} \right) = \left( {x + 2} \right)\left( {{x^2} - 2x + {2^2}} \right)$ ….. let it be eq. $\left( 2 \right)$
Now, we are going to substitute eq. $\left( 1 \right)$in eq.$\left( 2 \right)$ we will get :
$ \Rightarrow 4\left( {\left( {x + 2} \right)\left( {{x^2} - 2x + {2^2}} \right)} \right)$
Solve ${2^2}$ and put the value of it in the above equation:
$ \Rightarrow 4\left( {\left( {x + 2} \right)\left( {{x^2} - 2x + 4} \right)} \right)$
Now, by removing unnecessary parenthesis you will get to this:
$ \Rightarrow 4\left( {x + 2} \right)\left( {{x^2} - 2x + 4} \right)$
Hence, $4\left( {x + 2} \right)\left( {{x^2} - 2x + 4} \right)$is the required factored form of $4{x^3} + 32$.
Note: Look, we can factor further the term $\left( {{x^2} - 2x + 4} \right)$
The first term is, ${x^2}$ its coefficient is $1$.
The middle term is, $ - 2x$ its coefficient is $ - 2$.
The last term, “the constant”, is$ + 4$.
Now, multiply the coefficient of the first term by the last constant $1 \times 4 = 4$.
Finally, find two factors of 4 whose sum equals the coefficient of the middle term, which is $ - 2$.
As we cannot find any such two factors and therefore we can conclude that trinomial cannot be factored.
Then use the sum of cubes formula.
And factorize generally to achieve the solution.
Complete Step by Step Solution:
Let us start by writing the given equation:
$ \Rightarrow 4{x^3} + 32$
We will take out the common factor 4 out of $4{x^3}$ we get:
$ \Rightarrow 4\left( {{x^3}} \right) + 32$
Again take out the common factor 4 out of 32 we get:
$ \Rightarrow 4\left( {{x^3}} \right) + 4\left( 8 \right)$
Now, take out the common factor 4 out of the whole above equation we get:
$ \Rightarrow 4\left( {{x^3} + 8} \right)$
Rewrite 8 as ${2^3}$ we get:
$ \Rightarrow 4\left( {{x^3} + {2^3}} \right)$ ……. Let it be eq. $\left( 1 \right)$
Since, both terms are perfect cubes, factor using the sum of cubes formula:
$ \Rightarrow \left( {{a^3} + {b^3}} \right) = \left( {a + b} \right)\left( {{a^2} - ab + {b^2}} \right)$
Where, the values of the variables are as: $a = x$ and $b = 2$
Now substitute the values of a and b in the sum of cubes formula we will get:
$ \Rightarrow \left( {{x^3} + {2^3}} \right) = \left( {x + 2} \right)\left( {{x^2} - 2x + {2^2}} \right)$ ….. let it be eq. $\left( 2 \right)$
Now, we are going to substitute eq. $\left( 1 \right)$in eq.$\left( 2 \right)$ we will get :
$ \Rightarrow 4\left( {\left( {x + 2} \right)\left( {{x^2} - 2x + {2^2}} \right)} \right)$
Solve ${2^2}$ and put the value of it in the above equation:
$ \Rightarrow 4\left( {\left( {x + 2} \right)\left( {{x^2} - 2x + 4} \right)} \right)$
Now, by removing unnecessary parenthesis you will get to this:
$ \Rightarrow 4\left( {x + 2} \right)\left( {{x^2} - 2x + 4} \right)$
Hence, $4\left( {x + 2} \right)\left( {{x^2} - 2x + 4} \right)$is the required factored form of $4{x^3} + 32$.
Note: Look, we can factor further the term $\left( {{x^2} - 2x + 4} \right)$
The first term is, ${x^2}$ its coefficient is $1$.
The middle term is, $ - 2x$ its coefficient is $ - 2$.
The last term, “the constant”, is$ + 4$.
Now, multiply the coefficient of the first term by the last constant $1 \times 4 = 4$.
Finally, find two factors of 4 whose sum equals the coefficient of the middle term, which is $ - 2$.
As we cannot find any such two factors and therefore we can conclude that trinomial cannot be factored.
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