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9. Find the L.C.M. of: [tex]a^3-125[/tex] and [tex]a^4+25a^2+625[/tex]

Sagot :

Finding the Least Common Multiple (L.C.M.) of two polynomials involves determining the polynomial of the lowest degree that both given polynomials will divide without leaving a remainder. Here are the steps to find the L.C.M. of [tex]\(a^3 - 125\)[/tex] and [tex]\(a^4 + 25a^2 + 625\)[/tex]:

1. Factorize each polynomial:
- For [tex]\(a^3 - 125\)[/tex]:
[tex]\(a^3 - 125 = a^3 - 5^3\)[/tex]. This is a difference of cubes, which can be factorized using the formula [tex]\(a^3 - b^3 = (a - b)(a^2 + ab + b^2)\)[/tex]:
[tex]\[ a^3 - 125 = (a - 5)(a^2 + 5a + 25) \][/tex]

- For [tex]\(a^4 + 25a^2 + 625\)[/tex]:
Notice that [tex]\(a^4 + 25a^2 + 625\)[/tex] is a quadratic in terms of [tex]\(a^2\)[/tex]:
[tex]\(a^4 + 25a^2 + 625 = (a^2)^2 + 25(a^2) + 625\)[/tex].
This looks like a perfect square trinomial, [tex]\((A + B)^2 = A^2 + 2AB + B^2\)[/tex], but here it doesn't directly fit without crossing the middle term factor.
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Alternatively, we can approach this as a sum of squares form:
[tex]\[ a^4 + 25a^2 + 625 = (a^2 + 12.5 + 12.5i)(a^2 + 12.5 - 12.5i) \][/tex]

2. Combine the factorizations to find the L.C.M.:
- The L.C.M must include each distinct factor the maximum number of times it appears in any of the polynomials. In this content, let's gather the expanded factor presentation:

Upon expanding, it leads to a more concise combined factor representation.

The final L.C.M is:

[tex]\[ \boxed{a^5 - 5a^4 + 25a^3 - 125a^2 + 625a - 3125} \][/tex]

3. Verify by multiplication and division:
To ensure correctness, multiplying out factors to verify if it covers all terms in both polynomials given initially.

Combining the steps abstractly simplifies down to knowing factor overlaps and formulating the minimum coverage through polynomial LCM notions. Hence, the L.C.M. of [tex]\(a^3 - 125\)[/tex] and [tex]\(a^4 + 25a^2 + 625\)[/tex] correctly translates to:

[tex]\[ a^5 - 5a^4 + 25a^3 - 125a^2 + 625a - 3125 \][/tex]