Math Problem Statement

Express in simplest radical form with a rational denominator. start fraction, 4, plus, square root of, 7, end square root, divided by, 2, minus, square root of, 7, end square root, end fraction 2− 7 ​

4+ 7 ​

Solution

We are asked to simplify the following expression:

4+727\frac{4 + \sqrt{7}}{2 - \sqrt{7}}

To simplify, we need to rationalize the denominator. To do this, we multiply both the numerator and the denominator by the conjugate of the denominator. The conjugate of 272 - \sqrt{7} is 2+72 + \sqrt{7}.

Step 1: Multiply the numerator and denominator by 2+72 + \sqrt{7}:

4+7272+72+7=(4+7)(2+7)(27)(2+7)\frac{4 + \sqrt{7}}{2 - \sqrt{7}} \cdot \frac{2 + \sqrt{7}}{2 + \sqrt{7}} = \frac{(4 + \sqrt{7})(2 + \sqrt{7})}{(2 - \sqrt{7})(2 + \sqrt{7})}

Step 2: Simplify the denominator using the difference of squares formula:

(27)(2+7)=22(7)2=47=3(2 - \sqrt{7})(2 + \sqrt{7}) = 2^2 - (\sqrt{7})^2 = 4 - 7 = -3

So the denominator simplifies to 3-3.

Step 3: Expand the numerator:

(4+7)(2+7)=4(2)+4(7)+7(2)+7(7)(4 + \sqrt{7})(2 + \sqrt{7}) = 4(2) + 4(\sqrt{7}) + \sqrt{7}(2) + \sqrt{7}(\sqrt{7}) =8+47+27+7= 8 + 4\sqrt{7} + 2\sqrt{7} + 7 =15+67= 15 + 6\sqrt{7}

Step 4: Combine the numerator and denominator:

15+673\frac{15 + 6\sqrt{7}}{-3}

Step 5: Simplify by dividing both terms in the numerator by 3-3:

153+673=527\frac{15}{-3} + \frac{6\sqrt{7}}{-3} = -5 - 2\sqrt{7}

Thus, the expression in simplest radical form with a rational denominator is:

527-5 - 2\sqrt{7}

Would you like a detailed explanation of any step or have any questions?

Here are five related questions for practice:

  1. Rationalize the denominator: 5+232\frac{5 + \sqrt{2}}{3 - \sqrt{2}}
  2. Simplify: 7+32+3\frac{7 + \sqrt{3}}{2 + \sqrt{3}}
  3. Express in simplest form: 652+5\frac{6 - \sqrt{5}}{2 + \sqrt{5}}
  4. Rationalize and simplify: 1+646\frac{1 + \sqrt{6}}{4 - \sqrt{6}}
  5. Simplify: 3+858\frac{3 + \sqrt{8}}{5 - \sqrt{8}}

Tip: When rationalizing the denominator, always multiply by the conjugate to eliminate square roots from the denominator.

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Math Problem Analysis

Mathematical Concepts

Rationalization
Radicals
Conjugates
Algebra

Formulas

Difference of squares: (a - b)(a + b) = a^2 - b^2

Theorems

Difference of squares
Simplification of radical expressions

Suitable Grade Level

Grades 9-12