If a computer knows only one operation which is addition how does it perform subtraction?

Answer 1

Assuming the computer could operate addition of negative values the solution would be to add the additive inverse. For example, instead of subtracting 5 - 4 = 1, you would end the addition problem 5 + (-4) = 1. Note that in the second case the "-" was not a subtraction sign but rather a negative sign. In algebraic terms: If x - y = c then x + (-y) = c.

Answer 2

computers persform substraction by addition i.e substraction by 2'complement...
for instance,
if u want to substract 9 - 5
the first thing the computer will do is it will convert the numbers into its binary equivalent i.e.

9's binary equivalent is 1001 and
5's binary equivalent is 0101

then it negate the 0101 to 1010 (all zero's become one's & all one's become zero's)

then it will add the nine's binary equivalent 1001 with
the complement of 5's binary equivalent +1010
-----------------
the number we get is 1 0011
now we will make it 2's
complement by adding 1 1
----------------
0100 this binary equivalent of 4(9-5)


if you understand then send some feedback....

Answer 3

Don't know where you got the idea that computers can only add. Computers can perform all mathematic equasions by converting the numbers to binary form and performing the operation at a machine language level, then converting back to decimal or whatever number system you are using.

Answer 4

Computer can perform Both of them in binary level (0,1)multiplication and Division is done by using subtraction and addition property

Answer 5

it uses an additive inverse