What is 2y+-4y? it's to do with simultaneous equations

Exponents

Exponents are supported on variables using the ^ (caret) symbol. For example, to express x2, enter x^2. Note: exponents must be positive integers, no negatives, decimals, or variables. Exponents may not currently be placed on numbers, brackets, or parentheses.

Parentheses and Brackets

Parentheses () and brackets [ ] may be used to group terms as in a standard equation or expression.

Multiplication, Addition, and Subtraction

For addition and subtraction, use the standard + and - symbols respectively. For multiplication, use the * symbol. A * symbol is not necessiary when multiplying a number by a variable. For instance: 2 * x can also be entered as 2x. Similarly, 2 * (x + 5) can also be entered as 2 (x + 5); 2x * (5) can be entered as 2x (5). The * is also optional when multiplying with parentheses, example: (x + 1) (x - 1).

Order of Operations

The calculator follows the standard order of operations taught by most algebra books - Parentheses, Exponents, Multiplication and Division, Addition and Subtraction. The only exception is that division is not currently supported; attempts to use the / symbol will result in an error.

Division, Square Root, Radicals, Fractions

The above features are not supported at this time. A future release will add this functionality.

2y - 4y = 2y + - 4y = y+y + - y + - y + - y + - y = - y + - y = - 2