2x{\displaystyle 2x} is an expression. In this expression, you are multiplying the coefficient 2{\displaystyle 2} by the variable x{\displaystyle x}. 2x+3y{\displaystyle 2x+3y} is an expression called a binomial. In this expression, you add the product of 3y{\displaystyle 3y} to the product of 2x{\displaystyle 2x}. In this expression, 2{\displaystyle 2} and 3{\displaystyle 3} are coefficients, and x{\displaystyle x} and y{\displaystyle y} are variables. Once you add an equal sign to an expression, it becomes an equation. For example, 2x=14{\displaystyle 2x=14} is an equation.
For example, you might be asked to evaluate 2x{\displaystyle 2x} when x=2{\displaystyle x=2}.
For example, you might be asked to evaluate the expression 5x−10{\displaystyle 5x-10} when x=8{\displaystyle x=8}.
For example, to evaluate 5x−10{\displaystyle 5x-10} when x=8{\displaystyle x=8}, replace the x{\displaystyle x} in the equation with 8{\displaystyle 8}: 5(8)−10{\displaystyle 5(8)-10}.
For example:5(8)−10{\displaystyle 5(8)-10}=40−10{\displaystyle =40-10}=30{\displaystyle =30}So, 5(8)−10=30{\displaystyle 5(8)-10=30}.
Make sure you do not switch the values. The x{\displaystyle x} value cannot be substituted for the y{\displaystyle y} variable and vice versa. Doing so will give you an incorrect solution.
Identify the variable and its value. The variable is x{\displaystyle x}, and you are evaluating the expression for x=3{\displaystyle x=3}. Substitute the given value for the variable: 2(3)+3{\displaystyle 2(3)+3}. Make the necessary calculations: 2(3)+3=6+3=9{\displaystyle 2(3)+3=6+3=9}. Write the equation: 2(3)+3=9{\displaystyle 2(3)+3=9}
Identify both variables and their values. The variables are x{\displaystyle x} and y{\displaystyle y}, and you are evaluating the expression for x=2{\displaystyle x=2} and y=6{\displaystyle y=6}. Substitute both given values for the variables: 4(2)+3(6){\displaystyle 4(2)+3(6)}. Make the necessary calculations: 4(2)+3(6)=8+18=26{\displaystyle 4(2)+3(6)=8+18=26}. Write the equation: 4(2)+3(6)=26{\displaystyle 4(2)+3(6)=26}.
Identify the variable and its value. The variable is x{\displaystyle x}, and you are evaluating the expression for x=4{\displaystyle x=4}. Substitute the given value for the variable: 7(4)2−12(4)+13{\displaystyle 7(4)^{2}-12(4)+13}. Make the necessary calculations. Remember when working with exponents that you should calculate the exponent before multiplying by a coefficient:7(4)2−12(4)+13{\displaystyle 7(4)^{2}-12(4)+13}=7(16)−12(4)+13{\displaystyle =7(16)-12(4)+13}=112−48+13{\displaystyle =112-48+13}=64+13{\displaystyle =64+13}=77{\displaystyle =77} Write the equation: 7(16)−12(4)+13=77{\displaystyle 7(16)-12(4)+13=77}
