Answer:
x² + x + 6
Explanation:
We have to find the expression that must be added to (3x - 7) to make it (x² + 4x - 1).
To get the expression we have to subtract (3x - 7) from (x² + 4x - 1).
Now, (x² + 4x - 1) - (3x - 7)
= x² + x + 6
Therefore, (x² + x + 6) must be added to (3x - 7) to get the result (x² + 4x - 1).
So, the answer is x² + x + 6, which is in the descending power of x. (Answer)