Problem 66 - Algebra 2

Question

Simplify \(\left(9 x^{3}-4 x+2\right)-\left(x^{3}+3 x^{2}+1\right)\)

Step-by-Step Solution

Answer

\(8 x^{3} - 3 x^{2} - 4 x + 1\text{ is the simplified form of the given expression.}\)

Step 1: Distribute the Negative Sign

Start by distributing the negative sign (-) to the terms inside the second parentheses. This changes the signs of the terms inside the parentheses.

Step 2: Combine Like Terms

Combine the like terms by adding or subtracting the corresponding coefficients and keeping the same variable with its exponent if any.

Step 3: Write the Simplified Expression

Write down the simplified expression after combining like terms.

Key Concepts

Distributive Property

The distributive property is a key operation in algebra that allows us to multiply a single term by each term within a parenthesis. For example, when an expression like \( a(b + c) \) is given, the distributive property enables us to expand this into \( ab + ac \) by multiplying \( a \) with each term inside the parentheses.

However, it's not just about multiplication. The distributive property also applies to subtraction and addition in scenarios where you must distribute a negative sign across terms inside parentheses. In the provided exercise, \( -(x^{3}+3x^{2}+1) \) requires us to distribute the negative sign, effectively reversing the sign of each term within the parentheses, turning \( x^{3} \) into \( -x^{3} \) and so on. This use of the distributive property is crucial as it sets the stage for correctly simplifying the expression by ensuring that each term is accurately represented before combining like terms.

Combining Like Terms

Combining like terms is like organizing a pantry: you group similar items together to keep things tidy. In algebra, like terms are terms that have the same variables raised to the same power. Only the coefficients (the numbers in front of the variables) of these terms are added or subtracted.

When we look at the expression \(9x^{3} - 4x + 2 - x^{3} - 3x^{2} - 1\), we identify like terms by matching variable parts. Here, \(9x^{3}\) and \( -x^{3}\) are like terms, as are \( -4x\) and no other terms, since no other \(x\) terms without exponents are present. When combining, we add or subtract only the coefficients, giving \( (9 - 1)x^{3}\) for the cubic terms but leaving the \( -3x^{2}\) and linear term \( -4x\) untouched due to the lack of like terms to combine them with. Approached systematically, combining like terms simplifies expressions, making them neater and more manageable.

Polynomial Subtraction

Subtracting polynomials is a process resembling subtraction of multi-digit numbers, aligning each term precisely before taking away. Polynomial subtraction often uses both the distributive property and the principle of combining like terms discussed earlier.

To subtract one polynomial from another, write the polynomials one above the other, aligning like terms. Next, distribute the subtraction across each term of the second polynomial if needed, as shown in our exercise. Finally, subtract the coefficients of like terms to get the difference.

It's essential to watch the signs: a common pitfall is forgetting to distribute a negative sign to each term of the subtracted polynomial, leading to errors. Polynomials are subtracted correctly when each like term is accounted for with its respective sign. The final, simplified expression for the provided exercise is \(8x^{3} - 3x^{2} - 4x + 1\), neatly organized and ready for further mathematical manipulation or evaluation.