Problem 27 - Basic Technical Mathematics with Calculus

Question

solve the given quadratic equations, using the quadratic formula. Exercises \(5-8\) are the same as Exercises \(11-14\) of Section 7.2. $$15+4 z=32 z^{2}$$

Step-by-Step Solution

Answer

The solutions are \(z = \frac{3}{4}\) and \(z = \frac{-5}{8}\).

Step 1: 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.

Step 2: Identify coefficients

In the equation \(32z^2 - 4z - 15 = 0\), identify the coefficients: - \(a = 32\)- \(b = -4\)- \(c = -15\)

Step 3: 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.

Step 4: 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 \(= 16 + 1920 = 1936\)

Step 5: 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: \[ z = \frac{4 \pm 44}{64} \]

Step 6: 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 \(z = \frac{-5}{8}\).

Key Concepts

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:

• \( z = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \)

This singular formula derives roots from any quadratic equation provided you identify the correct coefficients \(a\), \(b\), and \(c\). It takes a little practice to get the hang of it, but once mastered, it's a powerful tool. The "\(\pm\)" in the formula allows us to find two potential solutions, reflecting the nature of quadratics to form parabolas that can intersect the \(z\)-axis in two places.

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:

• 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.

Calculating this correctly gives insight even before the complete solution, guiding expectations and helping in deeper analysis.

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:

• \( ax^2 + bx + c = 0 \)

Here, \(a\), \(b\), and \(c\) are constants with \(a eq 0\). Transitioning an equation to this form is usually the first step when utilizing methods like factoring, completing the square, or using the quadratic formula. The beauty of the standard form is in its consistency, allowing you to neatly plug in coefficients into the quadratic formula without complications. For our problem, rewriting it from \(15 + 4z = 32z^2\) to \(32z^2 - 4z - 15 = 0\) showcases this transformation, preparing it neatly for further analysis and solution.