The product of all solutions of the equation ( e^{(5*(\log_e x)^2) + 3} = x^8 ), ( x > 0 ), is: (1) ( e^{8/5} ) (2) ( e^{6/5} ) (3) ( e^2 ) (4) ( e )

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Published July 7, 2025
Mathematics
Algebra
Exponents_and_Logarithms
Quadratic_Equations

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Detailed Explanation

Key Ideas You Need

ConceptWhy it Matters Here
Natural Log (ln\ln)Converts a power of ee into a simple number you can add/subtract.
Taking ln\ln on Both SidesKeeps the equation balanced while removing the outer e  e^{\;} shell.
Substitution (y=lnxy = \ln x)Turns a messy expression into a clean quadratic.
Quadratic Formula / FactoringSolves for yy quickly.
Back-Substitution (x=eyx = e^y)Translates the yy answers back into xx.
Product of Roots in Same Base eeWhen two numbers are eae^{a} and ebe^{b}, their product is ea+be^{a+b}, so you just add exponents.

Logical Chain of Steps

  1. Recognise the variable in both exponent and base: xx sits inside ln\ln and also as a base (x8x^8).
  2. Remove the outer exponential by applying ln\ln to both sides. This is legal because x>0x>0 (domain of ln\ln).
  3. Use substitution y=lnxy = \ln x so the equation becomes a standard quadratic.
  4. Solve the quadratic using the discriminant or factoring.
  5. Convert back to xx by exponentiating (eye^y).
  6. Multiply the solutions; since both are powers of ee, simply add their exponents.

These six moves turn a daunting mixed log-exponential problem into a short, syllabus-friendly puzzle.

Simple Explanation (ELI5)

Imagine a See-Saw of Numbers

  1. Think of ln (log base e) as a magical magnifying glass that turns numbers into new ones so we can add or multiply them more easily.

  2. Our see-saw equation is

    e5(lnx)2+3=x8e^{5(\ln x)^2 + 3} = x^8

  3. Taking the ln on both sides is like peeking under the same magnifying glass on both ends of the see-saw so the balance is still fair.

  4. After this peek, the big scary power falls down to a neat quadratic (something that looks like ay2+by+c=0ay^2 + by + c = 0).

  5. Quadratics are like easy Lego bricks: solve for yy using the formula, then turn back (x=eyx = e^y) to get our original xx.

  6. Finally, multiply the two xx answers together. A fun surprise—you just add their exponents when the bases are both ee!

That’s it. 😊

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Step-by-Step Solution

Step-by-Step Solution

Given

e5(lnx)2+3=x8,x>0e^{5(\ln x)^2 + 3} = x^8, \quad x>0

  1. Take natural log on both sides

    ln ⁣(e5(lnx)2+3)=ln(x8)\ln\!\left(e^{5(\ln x)^2 + 3}\right) = \ln(x^8)

    5(lnx)2+3=8lnx5(\ln x)^2 + 3 = 8\,\ln x

  2. Substitute y=lnxy = \ln x.

    5y2+3=8y5y^2 + 3 = 8y

    Rearrange to standard quadratic:

    5y28y+3=05y^2 - 8y + 3 = 0

  3. Solve the quadratic

    Discriminant:

    Δ=(8)2453=6460=4\Delta = (-8)^2 - 4 \cdot 5 \cdot 3 = 64 - 60 = 4

    Roots:

    y=8±425=8±210y = \frac{8 \pm \sqrt{4}}{2 \cdot 5} = \frac{8 \pm 2}{10}

    y1=1010=1,y2=610=35y_1 = \frac{10}{10} = 1, \quad y_2 = \frac{6}{10} = \frac{3}{5}

  4. Back-substitute for xx

    x1=ey1=e1=ex_1 = e^{y_1} = e^1 = e

    x2=ey2=e3/5x_2 = e^{y_2} = e^{3/5}

  5. Product of the solutions

    x1×x2=e1e3/5=e1+3/5=e8/5x_1 \times x_2 = e^1 \cdot e^{3/5} = e^{1 + 3/5} = e^{8/5}

  6. Match with options
    Option (1): e8/5e^{8/5}

[\boxed{e^{8/5}}]

Examples

Example 1

Radioactive decay half-life calculations often use ln\ln to linearise an exponential curve.

Example 2

Compound interest problems simplify when you express growth factors as erte^{rt} and then take logs.

Example 3

Population growth models use substitution y=lnPy = \ln P to turn logistic equations into linear or quadratic forms.

Visual Representation

References

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