Verified Answer :

21 x³ + 35 x² + 9 x + 15 = 
= 7 x² ( 3 x + 5 ) + 3 ( 3 x + 5 ) =
= ( 3 x + 5 ) ( 7 x² + 3 )
That`s all. Thank you.

Answer:

The complete factored form of given polynomial  \(21x^3+35x^2+9x+15\) is \((7x^2+3)(3x+5)\)

Step-by-step explanation:

Given polynomial  \(21x^3+35x^2+9x+15\)

We have to factorize the given polynomial completely.

Consider the given polynomial  \(21x^3+35x^2+9x+15\)

We will solve it by grouping of terms,

Grouping is collecting terms having some factors common

Taking \(7x^2\) common from first two term and 3 from last two terms , we have,

\(21x^3+35x^2+9x+15\)

\(\Rightarrow 7x^2(3x+5)+3(3x+5)\)

Now taking (3x +5) common from both terms , we have,

\(\Rightarrow (7x^2+3)(3x+5)\)

Thus, the complete factored form of given polynomial  \(21x^3+35x^2+9x+15\) is \((7x^2+3)(3x+5)\)