-3y(x^2 + 4xy - 5y^2) = -3x^2y - 12xy^2 + 15y^3 - Groen Casting
Title: Solving the Equation –3y(x² + 4xy − 5y²) = −3x²y − 12xy² + 15y³ Step-by-Step
Title: Solving the Equation –3y(x² + 4xy − 5y²) = −3x²y − 12xy² + 15y³ Step-by-Step
Introduction
Understanding and simplifying algebraic equations is essential for students, researchers, and mathematics enthusiasts alike. One such equation—–3y(x² + 4xy − 5y²) = −3x²y − 12xy² + 15y³—can seem complex at first glance, but with a clear step-by-step breakdown, solving it becomes manageable. This article walks you through the full process of simplifying, expanding, and analyzing the equation to solve it clearly, alongside a practical example and key takeaways.
Understanding the Context
Understanding the Equation
We begin with:
–3y(x² + 4xy − 5y²) = −3x²y − 12xy² + 15y³
This is a bilinear equation in two variables x and y. The left-hand side (LHS) is a product involving y and a quadratic trinomial in x and y, while the right-hand side (RHS) is a cubic polynomial in x and y, including a pure cubic term in y³.
Rewriting the equation in standard form:
→ Move every term to the left-hand side:
–3y(x² + 4xy − 5y²) + 3x²y + 12xy² − 15y³ = 0
Key Insights
Step 1: Expand the Left Side
Distribute –3y across the parentheses:
–3y·x² − 3y·4xy + 3y·5y² + 3x²y + 12xy² − 15y³
→ –3x²y − 12xy² + 15y³ + 3x²y + 12xy² − 15y³
Step 2: Combine Like Terms
Group similar terms:
- x²y: (–3x²y + 3x²y) = 0
- xy²: (–12xy² + 12xy²) = 0
- y³: (15y³ – 15y³) = 0
Thus, the entire expression simplifies to:
0 = 0
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Step 3: Interpret the Result
Since both sides reduce to zero, the equation –3y(x² + 4xy − 5y²) = −3x²y − 12xy² + 15y³ is identically true for all real numbers x and y. In other words, the equation represents a trivial identity — it holds universally.
This means every ordered pair (x, y) satisfies the equation, and thus the expression is an algebraic identity.
Example Substitution (for clarity)
Choose x = 1, y = 2:
- LHS: –3(2)(1² + 4(1)(2) – 5(2)²) = –6(1 + 8 – 20) = –6(–11) = 66
- RHS: –3(1)²(2) – 12(1)(2)² + 15(2)³ = –6 – 48 + 120 = 66
✅ Both sides equal 66 — confirming the identity.
Why This Matters (Mathematical Insight)
Recognizing identities like this streamlines problem-solving. It avoids unnecessary algebraic steps and clarifies relationships between variables. Identities simplify calculus operations, parametric modeling, and error-checking in applied mathematics.
Key Takeaways
- Expand and simplify expressions carefully.
- Combine like terms accurately.
- Recognizing identical forms (like 0 = 0) indicates an identity.
- Substituting sample values verifies correctness.
- This equation is universally true for all real x, y.
