The notation
- 3a means 3 × a; ab means a × b.
- a² means a × a, and 3a² means 3 × a × a (only the a is squared). (3a)² is 9a².
- a/b means a ÷ b.
"5 more than twice n" is 2n + 5. "Twice the sum of n and 5" is 2(n + 5): the brackets show what happens first.
Substituting
Replace each letter with its number, in brackets, then follow the order of operations.
- x² − 3x + 4 when x = −2
- (−2)² − 3 × (−2) + 4
- = 4 + 6 + 4
- = 14
Brackets round negative numbers stop the two classic slips: (−2)² is 4, not −4, and −3 × (−2) is +6.
Check a substitution
Use the calculator: type (−2)^2 − 3 × (−2) + 4 with the brackets, then try it without the brackets around −2. Which one matches the working above?