Step 1 :
After factoring out $ x $ we have:
$$ 8x^{4}+x = x ( 8x^{3}+1 ) $$Step 2 :
To factor $ 8x^{3}+1 $ we can use sum of cubes formula:
$$ I^3 - II^3 = (I + II)(I^2 - I \cdot II + II^2) $$After putting $ I = 2x $ and $ II = 1 $ , we have:
$$ 8x^{3}+1 = ( 2x+1 ) ( 4x^{2}-2x+1 ) $$Step 3 :
Step 3: Identify constants $ a $ , $ b $ and $ c $.
$ a $ is a number in front of the $ x^2 $ term $ b $ is a number in front of the $ x $ term and $ c $ is a constant. In this case:
Step 4: Multiply the leading coefficient $\color{blue}{ a = 4 }$ by the constant term $\color{blue}{c = 1} $.
$$ a \cdot c = 4 $$Step 5: Find out two numbers that multiply to $ a \cdot c = 4 $ and add to $ b = -2 $.
Step 6: All pairs of numbers with a product of $ 4 $ are:
PRODUCT = 4 | |
1 4 | -1 -4 |
2 2 | -2 -2 |
Step 7: Find out which factor pair sums up to $\color{blue}{ b = -2 }$
Step 8: Because none of these pairs will give us a sum of $ \color{blue}{ -2 }$, we conclude the polynomial cannot be factored.