Chapter 5: Problem 76
Perform the operations. $$ (5 y-1)^{2}-(y+7)(y-7) $$
Short Answer
Expert verified
The simplified form is \(24y^{2} - 10y + 50\).
Step by step solution
01
Expand the first expression
Apply the formula for the square of a binomial: \[(a-b)^{2} = a^{2} - 2ab + b^{2}\]For our expression \((5y-1)^{2}\), let \(a=5y\) and \(b=1\). Then:\[(5y-1)^{2} = (5y)^{2} - 2(5y)(1) + (1)^{2} = 25y^{2} - 10y + 1\].
02
Expand the second expression
Use the difference of squares formula: \[(a+b)(a-b) = a^{2} - b^{2}\]For the expression \((y+7)(y-7)\), this gives:\[(y+7)(y-7) = y^{2} - 7^2 = y^{2} - 49\].
03
Substitute expanded expressions
Replace the original operations with the expanded forms obtained from the previous steps:\[(5y-1)^{2} - (y+7)(y-7) = (25y^{2} - 10y + 1) - (y^{2} - 49)\].
04
Simplify the expression
Distribute the negative sign across the second expanded expression and combine like terms:\[(25y^{2} - 10y + 1) - y^{2} + 49 = 25y^{2} - y^{2} - 10y + 1 + 49\].Combine like terms:\[24y^{2} - 10y + 50\].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Binomial Expansion
Binomial expansion is a critical algebraic skill that expands expressions raised to a power. Essentially, it involves using the Binomial Theorem to express powers of sums and differences as a sum of terms. One of the simplest forms is the expansion for a binomial squared:
Using this simple formula repeatedly will strengthen your understanding and make handling any squared binomial straightforward.
- The expression \((a-b)^2 = a^2 - 2ab + b^2\) illustrates how this works.
- Here, \(a\) and \(b\) are any two terms.
- This formula helps to break down and fully expand a squared binomial.
- First, calculate \((5y)^2 = 25y^2\).
- Second, compute \(-2 \times 5y \times 1 = -10y\).
- Finally, find \((1)^2 = 1\).
Using this simple formula repeatedly will strengthen your understanding and make handling any squared binomial straightforward.
Difference of Squares
The difference of squares is a special case in algebra that simplifies the multiplication of conjugates. It reflects a unique pattern:
- The formula \((a+b)(a-b) = a^2 - b^2\) captures this.
- It involves two terms squared and subtracted.
- Typically used to simplify multiplications where direct expansion might be cumbersome.
- Here, \(a = y\) and \(b = 7\).
- Thus, \((y+7)(y-7)\) simplifies to \(y^2 - 49\).
Polynomial Simplification
Polynomial simplification involves combining and reducing polynomial expressions to their simplest form. This process often follows expansion or factorization and involves:
- Distributing operations across terms.
- Combining like terms—terms with the same variable and exponent.
- To "simplify" is to collect all like terms.
- The expanded forms are \(25y^2 - 10y + 1\) and \(y^2 - 49\).
- Subtract the second from the first: \[(25y^2 - 10y + 1) - (y^2 - 49)\].
- Distribute the negative sign: \[25y^2 - y^2 - 10y + 49 + 1\].
- Finally, combine like terms to arrive at \(24y^2 - 10y + 50\).