The trick is to remember the remainder theorem which says that remainder equals f(c) if divisor is of the form x - c.
x+1 can be written as x - (-1) . So c = -1.
Another way of looking at it is to set x+1 = 0, then solve for x .x = -1
This is number you plug into f(x) to get remainder.
Ok, plug in -1 for x into x^245 - 3x^24 +5x + 4.
(-1) raised to any odd number will give -1
(-1) raised to any even number will give 1.
f(-1) = (-1) - 3(1) +5(-1) + 4
= -1 -3 -5 +4
= -5
Therefore, answer is -5.