Chapter 6: Problem 80
Solve. $$ 2(x-2)(x+3)=7 x-9 $$
Short Answer
Expert verified
The solutions are \(x = 3\) and \(x = -0.5\).
Step by step solution
01
Expand the Equation
First, we will expand the left side of the equation \(2(x-2)(x+3)\). Distribute \(2\) to both terms: \(2(x-2)(x+3) = 2((x-2)\cdot(x+3))\). Begin by expanding \((x-2)(x+3)\) using the distributive property: \[(x-2)(x+3) = x(x+3) - 2(x+3) \]Further simplify by distributing:\[x^2 + 3x - 2x - 6 = x^2 + x - 6 \]Now distribute \(2\) to each term:\[2(x^2 + x - 6) = 2x^2 + 2x - 12 \]
02
Simplify the Full Equation
With the left side simplified, the equation is:\[2x^2 + 2x - 12 = 7x - 9 \]Subtract \(7x\) and add \(9\) to both sides to set the equation to zero:\[2x^2 + 2x - 12 - 7x + 9 = 0 \]This simplifies to:\[2x^2 - 5x - 3 = 0 \]
03
Apply the Quadratic Formula
The equation obtained is a quadratic equation in the form \(ax^2 + bx + c = 0\). Here, \(a = 2\), \(b = -5\), and \(c = -3\). Use the quadratic formula:\[x = \frac{{-b \pm \sqrt{{b^2 - 4ac}}}}{2a} \]Substitute the values:\[x = \frac{{-(-5) \pm \sqrt{{(-5)^2 - 4\cdot2\cdot(-3)}}}}{2\cdot2} \]\[x = \frac{{5 \pm \sqrt{{25 + 24}}}}{4} \]\[x = \frac{{5 \pm \sqrt{49}}}{4} \]
04
Solve for x
Since \(\sqrt{49} = 7\), the solutions for \(x\) are:\[x = \frac{{5 + 7}}{4} \quad \text{or} \quad x = \frac{{5 - 7}}{4} \]Calculate each:\[x = \frac{12}{4} = 3 \quad \text{or} \quad x = \frac{-2}{4} = -0.5 \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Distributive Property
When tackling problems involving quadratic equations, the distributive property is a powerful and necessary tool. This property allows us to multiply a single term by each term in a binomial or polynomial expression. Think of it like distributing objects fairly among children at a party. In terms of algebra, we distribute a number or variable outside the parenthesis to every term inside the parenthesis.
In the exercise, we first applied the distributive property to expand \( (x-2)(x+3) \), meaning we wanted to multiply each term in \(x-2\) by each term in \(x+3\). This looks like:
In the exercise, we first applied the distributive property to expand \( (x-2)(x+3) \), meaning we wanted to multiply each term in \(x-2\) by each term in \(x+3\). This looks like:
- Multiply \(x\) by \(x+3\)
- Then multiply \(-2\) by \(x+3\)
Expanding Expressions
Expanding expressions is the process of eliminating the parentheses in an algebraic expression. This step is essential for simplifying complex equations and forms a core strategy when dealing with quadratic equations.
In our original problem, after using the distributive property, we expanded the expression \( (x-2)(x+3) \) to \( x^2 + x - 6 \). Here is how expanding helps:
In our original problem, after using the distributive property, we expanded the expression \( (x-2)(x+3) \) to \( x^2 + x - 6 \). Here is how expanding helps:
- It changes a product of sums or differences into a sum or difference of products, which is often more manageable.
- Expanding makes it easier to combine like terms, further simplifying the process.
Quadratic Formula
The quadratic formula is a trusty companion for solving quadratic equations, which are equations of the form \(ax^2 + bx + c = 0\). When factoring is not easy or possible, the quadratic formula steps in to solve for the variable.
To apply this formula, simply plug the coefficients (
In our exercise, using \(a = 2\), \(b = -5\), and \(c = -3\), we calculated the solutions as \(x = 3\) and \(x = -0.5\). This formula allows us to find solutions effectively, even when equations get tricky.
To apply this formula, simply plug the coefficients (
- \(a\) - the coefficient of \(x^2\)
- \(b\) - the coefficient of \(x\)
- \(c\) - the constant term
In our exercise, using \(a = 2\), \(b = -5\), and \(c = -3\), we calculated the solutions as \(x = 3\) and \(x = -0.5\). This formula allows us to find solutions effectively, even when equations get tricky.