∫| b | = 5 ∴b=-5 or 5

Then a+b=-4+5= 1

a+b=-4+(-5)=-9

a+b=4+5=9

a+b=4+(-5)=- 1

∴ There are four values 1,-1, 9, -9.

When you encounter the above problems, you should first judge the value of this number. The absolute value of a number may be its inverse, and then the calculation begins.

I think you are in grade one. Listen carefully in class. If such a small topic is wrong, you will not get satisfactory results in the mid-term and final exams. I suggest that you read this book carefully before doing any exercises and master the methods of doing them. I wish you good results in the midterm.