Welcome, math explorers! 🚀 Today we are going to learn how to speak the secret language of math. Let's dive in!
Imagine you have a magic box of toys, but you don't know exactly how many toys are inside. Instead of drawing a question mark, mathematicians use a letter from the alphabet (like x, y, or a) to stand for that mystery number. We call this letter a variable!
An algebraic expression is like a math sentence. It combines our mystery letters, normal numbers, and math symbols like plus (+) and minus (-).
Math Translation Guide:
Words like "sum", "more than", or "increased by" mean ADD (+).
Words like "difference", "less than", or "decreased by" mean SUBTRACT (-).
Example 1: Write an expression for "a number plus four".
Answer: Let's use x for the number. The expression is x + 4.
Example 2: Write an expression for "a number decreased by two".
Answer: Let's use y. Decreased by means subtract, so it's y - 2.
Example 3: What is the constant in the expression m + 10?
Answer: 10 is the constant because it's the normal number.
Click on your answer. Blue means Correct, Red means Incorrect!
Substitution is when we finally discover what the mystery number is! Once we know the secret value of our variable, we can swap the letter out for the number and solve the puzzle.
Think of substitution like a substitute teacher. If your regular teacher (the variable) is away, a substitute (the number) takes their exact place!
Steps for Substitution:
1️⃣ Write down the expression.
2️⃣ Swap the variable for the number you are given.
3️⃣ Do the math!
Example 1: Evaluate x + 3 when x = 5.
Answer:
Step 1: Swap the x for 5.
Step 2: The problem becomes 5 + 3.
Step 3: 5 + 3 = 8.
Example 2: Evaluate y - 4 when y = 10.
Answer:
Step 1: Swap the y for 10.
Step 2: The problem becomes 10 - 4.
Step 3: 10 - 4 = 6.