# 1.05 Equations involving addition or subtraction.

For equations that only involve addition or subtraction e.g. ,

• x = y - z ,
• A = B + C ,

there is another simple rule for moving individual symbols.

• If a symbol is positive then it becomes negative when moved across to the other side and vice versa.

Examples.

• If x = y - z , then x + z = y .
• If A = B + C , then A - C = B .
• Also If A = B + C , then A - B = C .

Combining the previous two rules.
If an equation involves both multiplication and division as well as addition and subtraction:

1. The rule for multiplication and division can be used with terms that are connected by + or - signs, but all terms must be moved together, as if they were bound together by brackets.
2. The rule for addition and subtraction can be used with terms that are multiplied or divided, but again, all terms must be moved together, as if they were bound together by brackets.

Examples.

1:a      A = B/(C + D) ,      A(C+D) = B .
1:b      P(Q - R)= S ,         P = S/(Q - R).

2:a      A -BC = D ,         A = BC +D .
2:b      AB + CD = EF ,   AB = EF - CD .