A letter represents a number whose value may vary or is not yet known. In 3a2b, the coefficient is 3, and a2 means a x a. Multiplication signs are usually omitted: ab=a x b. A fraction bar groups its whole numerator and denominator: a+bc=(a+b) c, where c 0. An expression has no equality to solve. An equation states that two expressions are equal. To evaluate an expression, substitute the values, use brackets for negative numbers, and follow the order of operations. Example For a=-2 and b=3, 3a2b=3(-2)2(3)=36. In contrast, -a2=-4: the square is evaluated before the minus sign. If one notebook costs p dollars, buying n notebooks and paying a delivery fee of 4 dollars costs np+4 dollars. The fee is added once, not once per notebook.

A letter represents a number whose value may vary or is not yet known. In \(3a^2b\), the coefficient is \(3\), and \(a^2\) means \(a\times a\). Multiplication signs are usually omitted: \(ab=a\times b\). A fraction bar groups its whole numerator and denominator: \(\dfrac{a+b}{c}=(a+b)\div c\), where \(c\ne0\).

An expression has no equality to solve. An equation states that two expressions are equal. To evaluate an expression, substitute the values, use brackets for negative numbers, and follow the order of operations.

For \(a=-2\) and \(b=3\), \(3a^2b=3(-2)^2(3)=36\). In contrast, \(-a^2=-4\): the square is evaluated before the minus sign.

If one notebook costs \(p\) dollars, buying \(n\) notebooks and paying a delivery fee of \(4\) dollars costs \(np+4\) dollars. The fee is added once, not once per notebook.

Letters, expressions and substitution

Letters, expressions and substitution