Given:
The trinomial equation is given as,
The objective is to choose the correct value for which the factors are to be obtained for factorization.
Step-by-step explanation:
From the step 1, to perform the factorization the values of a and c has to be multiplied.
Then in step 2, the factors need to be calculated for the product of a and c.
Product of a and c :
The product of a and c will be,
Thus, factors are to be listed for the number 21.
Hence, option (1) is the correct answer.