Problem 29 - Elementary Algebra

Question

For the following problems, find the products. $$ (3 a-9)^{2} $$

Step-by-Step Solution

Answer

Answer: The product of the given expression is $(3a - 9)^2 = 9a^2 - 54a + 81$.

Step 1: Identify A and B

In our expression, we have \(A = 3a\) and \(B = 9\).

Step 2: Apply the square of binomial formula

We can now write the expression using the formula: $$(3a - 9)^2 = (3a)^2 - 2(3a)(9) + (9)^2$$

Step 3: Calculate the terms

Next, we'll calculate each term: $$(3a)^2 = 9a^2$$ $$2(3a)(9) = 54a$$ $$(9)^2 = 81$$

Step 4: Express the final result

Replace the terms back into our expression: $$(3a - 9)^2 = 9a^2 - 54a + 81$$ The product of the given expression is: $$ (3a - 9)^2 = 9a^2 - 54a + 81 $$

Key Concepts

Binomial Theorem

The binomial theorem is a powerful algebraic tool that describes the expansion of expressions raised to a power. It allows us to expand expressions like \( (a + b)^n \) without multiplying them out repeatedly. The theorem states that:\[ (a + b)^n = \sum_{k=0}^{n} \binom{n}{k} a^{n-k} b^{k} \]where \( \binom{n}{k} \) are the binomial coefficients calculated as:\[ \binom{n}{k} = \frac{n!}{k!(n-k)!} \]This can be especially useful for expanding higher degree polynomial expressions, as it provides a clear formula to directly calculate each term in the expansion. To apply the binomial theorem effectively, identify the components \( a \) and \( b \) in your expression, as well as the power \( n \), and then use the formula to expand the polynomial.

Polynomial Expansion

Polynomial expansion is the process of breaking down expressions like \( (3a - 9)^2 \) into a sum of simpler terms. When expanding polynomials, it's important to understand the structure of the expansion and use the correct algebraic formulas. In this exercise, we use the square of a binomial formula:\[ (A - B)^2 = A^2 - 2AB + B^2 \]This formula helps in decomposing the given expression into individual terms such as \( A^2 \), \( -2AB \), and \( B^2 \). With each of these terms calculated separately, they can then be added together to form the expanded polynomial. Practicing this process not only enhances algebraic manipulation skills but also deepens the understanding of polynomial relationships. And remember, expanding polynomials accurately is essential in solving equations and modeling real-world scenarios.

Quadratic Expressions

Quadratic expressions are polynomial expressions of the form \( ax^2 + bx + c \), where \( a, b, ext{ and } c \) are coefficients, and \( a \) is not zero. These expressions are vital in understanding a vast range of mathematical phenomena, including parabolic graphs and solving quadratic equations.In this particular problem, the expanded form \( 9a^2 - 54a + 81 \) is a quadratic expression. Every quadratic expression has a characteristic shape, a parabola when graphed, and is defined by its vertex and the direction it opens (upward or downward). These expressions not only appear frequently in algebra but also in calculus, physics, and engineering.Key elements include: - **Leading Coefficient**: Determines the parabola's width and direction. - **Constant Term**: Indicates where the parabola intersects the y-axis. - **Classification by Factoring**: Useful in finding roots or solutions to the quadratic.Understanding how to work with quadratic expressions is fundamental for mathematics advancement and is applicable in various scientific and real-world contexts.