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Question

Find the difference between the values of ‘m’ for which $2m = 5\sqrt{m} - 2$.

The correct answer is
$\frac{15}{4}$

Solving the Radical Equation for 'm'

The problem asks for the difference between the values of 'm' that satisfy the equation $2m = 5\sqrt{m} - 2$. We need to solve this equation first.

Transforming the Equation

Let $x = \sqrt{m}$. This substitution requires $x \ge 0$. Since $m = x^2$, we can rewrite the equation in terms of $x$. Substituting $m = x^2$ and $\sqrt{m} = x$ into the original equation yields:

$2x^2 = 5x - 2$

Solving the Quadratic Equation

Rearrange the equation into the standard quadratic form $ax^2 + bx + c = 0$:

$2x^2 - 5x + 2 = 0$

This quadratic equation can be solved by factoring:

  • Find two numbers that multiply to $(2)(2) = 4$ and add to $-5$. These are $-4$ and $-1$.
  • Rewrite the middle term: $2x^2 - 4x - x + 2 = 0$.
  • Factor by grouping: $2x(x - 2) - 1(x - 2) = 0$.
  • Factor out the common binomial factor $(x - 2)$: $(2x - 1)(x - 2) = 0$.

Setting each factor to zero gives the possible values for $x$:

$2x - 1 = 0 \implies x = \frac{1}{2}$

$x - 2 = 0 \implies x = 2$

Both solutions $x = \frac{1}{2}$ and $x = 2$ are valid because they satisfy the condition $x \ge 0$.

Finding the Values of 'm'

Convert the values of $x$ back to values of 'm' using the substitution $x = \sqrt{m}$:

  • If $x = \frac{1}{2}$, then $\sqrt{m} = \frac{1}{2}$. Squaring both sides gives $m = (\frac{1}{2})^2 = \frac{1}{4}$.
  • If $x = 2$, then $\sqrt{m} = 2$. Squaring both sides gives $m = 2^2 = 4$.

Both $m = \frac{1}{4}$ and $m = 4$ are solutions to the original radical equation.

Calculating the Difference

The final step is to find the difference between the two values of 'm':

Difference = $|4 - \frac{1}{4}| = |\frac{16}{4} - \frac{1}{4}| = |\frac{15}{4}| = \frac{15}{4}$.

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Important Questions from Quadratic equation

  1. What number should be subtracted from x3−4x2−8x+11 to make the number divisible by (x+2)?

  2. Find the value of K if the quadratic equations $2x^2 + Kx + 8 = 0$ and $3x^2 + 4x + 12 = 0$ have both roots common.
  3. If sum and product of the roots of a quadratic equation are $(4-3\sqrt{2})$ and -28, respectively, then find the quadratic equation.
  4. If the quadratic equations $4x^2 + bx + 3 = 0$ and $8x^2 + 4x + c = 0$ have both the roots common, find the values for b and c, respectively.
  5. Determine the nature of the roots of the quadratic equation $3x^2 + 2x + 5 = 0$.
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