Chapter 7: Problem 27
solve the given quadratic equations, using the quadratic formula. Exercises \(5-8\) are the same as Exercises \(11-14\) of Section 7.2. $$15+4 z=32 z^{2}$$
Short Answer
Expert verified
The solutions are \(z = \frac{3}{4}\) and \(z = \frac{-5}{8}\).
Step by step solution
01
Rewrite the equation in standard form
The given equation is \(15 + 4z = 32z^2\). To use the quadratic formula, we first need to write it in the standard quadratic form, \(ax^2 + bx + c = 0\). Subtract \(4z\) and \(15\) from both sides to get: \[ 32z^2 - 4z - 15 = 0 \] Now we have the standard form.
02
Identify coefficients
In the equation \(32z^2 - 4z - 15 = 0\), identify the coefficients: - \(a = 32\)- \(b = -4\)- \(c = -15\)
03
Write the quadratic formula
The quadratic formula is: \[ z = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \]We will apply this formula with the values we identified.
04
Calculate the discriminant
First, calculate the discriminant \(b^2 - 4ac\):- \(b^2 = (-4)^2 = 16\)- \(4ac = 4 \times 32 \times (-15) = -1920\)- Discriminant \(= 16 - (-1920)\)- Discriminant \(= 16 + 1920 = 1936\)
05
Calculate the roots
With the discriminant from step 4, compute the roots:- \(\sqrt{1936} = 44\)- Using the quadratic formula: \[ z = \frac{-(-4) \pm 44}{2 \times 32} \] Simplify to: \[ z = \frac{4 \pm 44}{64} \]
06
Solve for both values of z
Calculate \(z\) for both \(+\) and \(-\) cases:For \(+\): \[ z = \frac{4 + 44}{64} = \frac{48}{64} = \frac{3}{4} \]For \(-\): \[ z = \frac{4 - 44}{64} = \frac{-40}{64} = \frac{-5}{8} \]Thus, the solutions are \(z = \frac{3}{4}\) and \(z = \frac{-5}{8}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
quadratic formula
When faced with a quadratic equation, such as the one we've been exploring, finding the solutions can be seamless using the quadratic formula. This reliable formula is a staple in algebra. It neatly handles equations in the standard form, allowing us to determine the values of the variable. The quadratic formula is as follows:
- \( z = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \)
discriminant
The discriminant plays a pivotal role in understanding the nature of the solutions of a quadratic equation. It is the part of the quadratic formula under the square root, specifically \(b^2 - 4ac\).
This important component tells us how many solutions we can expect and their type:
This important component tells us how many solutions we can expect and their type:
- A positive discriminant (>0) indicates two distinct real roots.
- A zero discriminant (=0) results in exactly one real root, revealing a tangent where the parabola just touches the \(z\)-axis.
- A negative discriminant (<0) signals no real root, but instead two complex roots.
standard form
The standard form of a quadratic equation is crucial as it establishes a starting point for solving the equation. The standard form is expressed as:
- \( ax^2 + bx + c = 0 \)