Are the expressions $8 a^2-4 b+7 a^2$ and $15 a^2-10 b+6 b$ equivalent? Explain your reasoning.
To determine if two algebraic expressions are equivalent, we need to check if they have the same value for all possible values of the variables. This is most easily done by simplifying both expressions by combining like terms. Like terms are terms that have the same variables raised to the same powers. In our case, the terms involved are \(a^2\) and \(b\).
We first simplify the expression \(8a^2 - 4b + 7a^2\).
To do this, we group the terms that contain \(a^2\):
\[8a^2 + 7a^2 - 4b\]
Adding the coefficients of \(a^2\) gives \(8 + 7 = 15\). Thus, the expression becomes:
\[15a^2 - 4b\]
Next, we simplify the expression \(15a^2 - 10b + 6b\).
Here, we group the terms that contain \(b\):
\[15a^2 + (-10b + 6b)\]
Combining the coefficients of \(b\), we have \(-10 + 6 = -4\). Thus, the expression becomes:
\[15a^2 - 4b\]
Comparing the simplified forms of both expressions, we see that both simplify to exactly \(15a^2 - 4b\). Since both expressions reduce to the same polynomial, they are equivalent for all values of \(a\) and \(b\). Therefore, the answer is yes, they are equivalent. \(\boxed{\text{Yes}}\)
Algebraic equivalence is a fundamental concept in mathematics that helps in simplifying complex equations and verifying solutions. For instance, if you are designing a budget for a project and calculate costs using two different formulas—such as total cost as 5 units of labor + 3 units of materials versus 2 units of labor + 3 units of materials + 3 units of labor—understanding that these expressions are equivalent confirms that your accounting is consistent regardless of how you group the items. This ability to manipulate expressions ensures that calculations remain accurate during complex problem-solving.