Answer: The correct option is (A) 3x + 5.
Step-by-step explanation: We are given to select the correct factor of the following quadratic expression :
[tex]E=9x^2+21x+10[/tex]
To factorize the given expression, we must find two numbers whose sum is 21 and product is 90.
The factorization of the given expression is as follows :
[tex]E\\\\=9x^2+21x+10\\\\=9x^2+15x+6x+10\\\\=3x(3x+5)+2(3x+5)\\\\=(3x+2)(3x+5).[/tex]
Therefore, the required factors of the given expression are (3x + 2) and (3x + 5).
Thus, the factor (3x + 5) is the correct one.
Hence, option (A) is CORRECT.
