When I teach ACT and SAT classes, I find that the most intimidating math topic is always the Symbolic Function. The complaints are inevitable: "But I don't know what an upside down triangle even means!" or "I've never seen this in school!" or "Does a star inside of a circle mean multiply? I just don't understand!"We are programmed to believe that symbols in math demand a specific action from us (multipy, divide, add, subtract, square, etc.), so it's difficult for us to accept the truth about symbolic functions: the symbols themselves do not signal any definitive operation. They are simply an announcement, yelling, "Hey, I'm a function!" If a symbolic function uses a diamond, it doesn't matter if I replace the diamond with a circle, star, square, or four-leaf clover; the question will be solved exactly the same way, no matter what symbol is chosen to announce the presence of a function.
Let's look at an example:
It may help to think of all function questions as having a ‘puzzle’ and a ‘key.’ The puzzle involves the original equation:
The key is the portion of the question that places new expressions or terms into the function:
To solve these questions, align the key directly below the puzzle:
The key reveals that x = 4 and y = 8. In the puzzle, substitute a 4 for every x and an 8 for every y:
Then solve the equation:
The correct answer is (C).
Alignment is extremely important, especially when the key involves expressions:
For every g, substitute the expression x + 3. For every h, substitute x – 4. Use parentheses for the expressions so that you remember to distribute any negatives or exponents:
Using proper alignment can save you from careless mistakes on the ACT and SAT.Need some more help? Check out our ACT courses and tutoring!
Photo: "Signs_Symbols," courtesy of Liga Eglite