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Write the following as a single fraction in its simplest form - Junior Cycle Mathematics - Question 12 - 2021

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Write the following as a single fraction in its simplest form. $$\frac{2}{n - 3} - \frac{5}{2n + 5}$$ Show that $$ (4x - 3)^2 + 24x $$ is positive for all values o... show full transcript

Worked Solution & Example Answer:Write the following as a single fraction in its simplest form - Junior Cycle Mathematics - Question 12 - 2021

Step 1

Write the following as a single fraction in its simplest form.

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Answer

To combine the two fractions, we will use a common denominator. The common denominator is (n3)(2n+5)(n - 3)(2n + 5).

  1. Rewrite the fractions:

    2n3=2(2n+5)(n3)(2n+5)\frac{2}{n - 3} = \frac{2(2n + 5)}{(n - 3)(2n + 5)}

    and

    52n+5=5(n3)(n3)(2n+5)\frac{5}{2n + 5} = \frac{5(n - 3)}{(n - 3)(2n + 5)}.

  2. Combine the fractions:

    2(2n+5)5(n3)(n3)(2n+5)\frac{2(2n + 5) - 5(n - 3)}{(n - 3)(2n + 5)}.

  3. Simplify the numerator:

    2(2n+5)5(n3)=4n+105n+15=n+252(2n + 5) - 5(n - 3) = 4n + 10 - 5n + 15 = -n + 25.

Thus, we have:

n+25(n3)(2n+5)\frac{-n + 25}{(n - 3)(2n + 5)}.

In its simplest form, the answer is:

n+25(n3)(2n+5)\frac{-n + 25}{(n - 3)(2n + 5)}.

Step 2

Show that (4x - 3)^2 + 24x is positive for all values of x ∈ R.

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Answer

To demonstrate that (4x3)2+24x(4x - 3)^2 + 24x is positive, we first expand the expression:

  1. Expanding the squared term:

    (4x3)2=16x224x+9(4x - 3)^2 = 16x^2 - 24x + 9.

  2. Substituting this back into the expression gives:

    16x224x+9+24x=16x2+916x^2 - 24x + 9 + 24x = 16x^2 + 9.

  3. Notice that 16x216x^2 is always non-negative (it is a squared term) and adds a positive value, 9:

    16x2+9>016x^2 + 9 > 0 for all xR x \in \mathbb{R}.

Thus, we can conclude that the entire expression is positive for all real values of xx.

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