Math Problem Statement

Find the least common multiple of the expressions below. Once found, determine the quantities with which you need to multiply each expression in order to obtain the least common multiple. (a) x and x + 3. (b) x2 + 6x − 16 and x2 + 9x + 14. (c) x3 − 36x and x2 + 2x − 24. (d) x2 + 2tx − 3t2 and x2 − t2.

Solution

(a) xx and x+3x + 3

  • LCM of xx and x+3x + 3: Since these two expressions are linear and distinct, their least common multiple is simply their product.

    LCM(x,x+3)=x(x+3)\text{LCM}(x, x + 3) = x(x + 3)

  • Multiplying factors:

    • To make xx into the LCM, you need to multiply xx by (x+3)(x + 3).
    • To make x+3x + 3 into the LCM, you need to multiply x+3x + 3 by xx.

(b) x2+6x16x^2 + 6x - 16 and x2+9x+14x^2 + 9x + 14

First, factor both quadratic expressions.

  • x2+6x16x^2 + 6x - 16 factors as (x2)(x+8)(x - 2)(x + 8).

  • x2+9x+14x^2 + 9x + 14 factors as (x+2)(x+7)(x + 2)(x + 7).

  • LCM of x2+6x16x^2 + 6x - 16 and x2+9x+14x^2 + 9x + 14: To find the LCM, we take the product of all distinct linear factors, raised to their highest powers:

    LCM(x2+6x16,x2+9x+14)=(x2)(x+8)(x+2)(x+7)\text{LCM}(x^2 + 6x - 16, x^2 + 9x + 14) = (x - 2)(x + 8)(x + 2)(x + 7)

  • Multiplying factors:

    • To make x2+6x16x^2 + 6x - 16 into the LCM, you need to multiply it by (x+2)(x+7)(x + 2)(x + 7).
    • To make x2+9x+14x^2 + 9x + 14 into the LCM, you need to multiply it by (x2)(x+8)(x - 2)(x + 8).

(c) x336xx^3 - 36x and x2+2x24x^2 + 2x - 24

First, factor both expressions.

  • x336x=x(x6)(x+6)x^3 - 36x = x(x - 6)(x + 6).

  • x2+2x24x^2 + 2x - 24 factors as (x6)(x+4)(x - 6)(x + 4).

  • LCM of x336xx^3 - 36x and x2+2x24x^2 + 2x - 24: To find the LCM, we take the product of all distinct linear factors, raised to their highest powers:

    LCM(x336x,x2+2x24)=x(x6)(x+6)(x+4)\text{LCM}(x^3 - 36x, x^2 + 2x - 24) = x(x - 6)(x + 6)(x + 4)

  • Multiplying factors:

    • To make x336xx^3 - 36x into the LCM, you need to multiply it by (x+4)(x + 4).
    • To make x2+2x24x^2 + 2x - 24 into the LCM, you need to multiply it by x(x+6)x(x + 6).

(d) x2+2tx3t2x^2 + 2tx - 3t^2 and x2t2x^2 - t^2

First, factor both expressions.

  • x2+2tx3t2x^2 + 2tx - 3t^2 factors as (x+3t)(xt)(x + 3t)(x - t).

  • x2t2x^2 - t^2 is a difference of squares and factors as (x+t)(xt)(x + t)(x - t).

  • LCM of x2+2tx3t2x^2 + 2tx - 3t^2 and x2t2x^2 - t^2: To find the LCM, we take the product of all distinct linear factors, raised to their highest powers:

    LCM(x2+2tx3t2,x2t2)=(x+3t)(x+t)(xt)\text{LCM}(x^2 + 2tx - 3t^2, x^2 - t^2) = (x + 3t)(x + t)(x - t)

  • Multiplying factors:

    • To make x2+2tx3t2x^2 + 2tx - 3t^2 into the LCM, you need to multiply it by (x+t)(x + t).
    • To make x2t2x^2 - t^2 into the LCM, you need to multiply it by (x+3t)(x + 3t).

Let me know if you want further details or have any questions!

Here are 5 questions related to the problem:

  1. What is the difference between the least common multiple and greatest common divisor?
  2. How do you factor cubic polynomials like x336xx^3 - 36x?
  3. Why is factoring necessary when determining the least common multiple of polynomials?
  4. Can a least common multiple of two polynomials be simpler than their product?
  5. How can the LCM concept be extended to more than two polynomials?

Tip: Always check the factorization of each expression carefully to ensure accuracy when calculating the LCM!

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Math Problem Analysis

Mathematical Concepts

Algebra
Polynomials
Factoring
Least Common Multiple (LCM)

Formulas

LCM of polynomials: product of distinct linear factors raised to their highest powers
Factoring quadratic polynomials: ax^2 + bx + c = (px + q)(rx + s)

Theorems

Fundamental Theorem of Algebra
Factoring Theorem for Polynomials

Suitable Grade Level

Grades 10-12