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Question

Find the value of $\frac{x+3}{x^2-2x} \times \frac{2x-1}{x^2+2x+4} \times \frac{x^4-8x}{2x^2+5x-3}$

The correct answer is
1

The problem asks to simplify the product of three rational algebraic fractions.

Factor Each Expression

To simplify the product, we first factor each numerator and denominator:

  • First fraction: $\frac{x+3}{x^2-2x}$
    • Numerator: $x+3$ (already factored)
    • Denominator: $x^2-2x = x(x-2)$
  • Second fraction: $\frac{2x-1}{x^2+2x+4}$
    • Numerator: $2x-1$ (already factored)
    • Denominator: $x^2+2x+4$ (irreducible over real numbers, related to difference of cubes)
  • Third fraction: $\frac{x^4-8x}{2x^2+5x-3}$
    • Numerator: $x^4-8x = x(x^3-8)$. Using the difference of cubes formula $a^3-b^3 = (a-b)(a^2+ab+b^2)$, we get $x^3-8 = x^3-2^3 = (x-2)(x^2+2x+4)$. So, the numerator is $x(x-2)(x^2+2x+4)$.
    • Denominator: $2x^2+5x-3$. We look for two numbers that multiply to $2 \times -3 = -6$ and add to $5$. These are $6$ and $-1$. So, $2x^2+6x-x-3 = 2x(x+3)-1(x+3) = (2x-1)(x+3)$.

Rewrite and Simplify Product

Now, substitute the factored forms back into the expression:

$ \frac{x+3}{x(x-2)} \times \frac{2x-1}{x^2+2x+4} \times \frac{x(x-2)(x^2+2x+4)}{(2x-1)(x+3)} $

Cancel out the common factors in the numerators and denominators:

  • The term $(x+3)$ cancels out.
  • The term $x$ cancels out.
  • The term $(x-2)$ cancels out.
  • The term $(2x-1)$ cancels out.
  • The term $(x^2+2x+4)$ cancels out.

After canceling all common factors, the expression simplifies to:

$ 1 $

Therefore, the value of the given expression is 1.

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Important Questions from Algebra (Notes)

  1. If $(y-12) = 4\sqrt{5}$, then find the value of $\sqrt{y-3} - \frac{1}{\sqrt{y-3}}$.
  2. If $x^2 + \frac{1}{x^2} = 16$ and $x \neq 0$, then what is the value of $x^4 + \frac{1}{x^4}$?
  3. In the expansion of (x + 9)(x - 6)(x + 5), what is the coefficient of x?
  4. The roots of the equation $ax^3-24x^2+188x-480=0$ are three consecutive even natural numbers. The value of a is _____.
  5. If $a = 0.1125$, then find the value of $100\left[\sqrt{1 + 2(3a) + 9a^2} - 4a\right]$.
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