Math Problem Statement

Rationalize the denominator and simplify the expression completely: (5i) / (-2 - 6i).

Solution

The problem in the image asks to rationalize the denominator and simplify the expression completely. The given expression is:

5i26i\frac{5i}{-2 - 6i}

To rationalize the denominator, we multiply both the numerator and denominator by the complex conjugate of the denominator, which is 2+6i-2 + 6i. The complex conjugate is used because multiplying a complex number by its conjugate results in a real number.

So, multiply the fraction by 2+6i2+6i\frac{-2 + 6i}{-2 + 6i}:

5i26i×2+6i2+6i=5i(2+6i)(26i)(2+6i)\frac{5i}{-2 - 6i} \times \frac{-2 + 6i}{-2 + 6i} = \frac{5i(-2 + 6i)}{(-2 - 6i)(-2 + 6i)}

Now let's expand both the numerator and denominator.

Numerator: 5i(2+6i)=5i(2)+5i(6i)=10i+30i25i(-2 + 6i) = 5i(-2) + 5i(6i) = -10i + 30i^2 Since i2=1i^2 = -1, we get: 10i+30(1)=10i30-10i + 30(-1) = -10i - 30 So the numerator is 3010i-30 - 10i.

Denominator: (26i)(2+6i)=(2)2(6i)2=436i2(-2 - 6i)(-2 + 6i) = (-2)^2 - (6i)^2 = 4 - 36i^2 Since i2=1i^2 = -1, we get: 436(1)=4+36=404 - 36(-1) = 4 + 36 = 40

Thus, the expression becomes: 3010i40\frac{-30 - 10i}{40}

Now simplify the fraction: 304010i40=34i4\frac{-30}{40} - \frac{10i}{40} = -\frac{3}{4} - \frac{i}{4}

So the simplified expression is: 34i4-\frac{3}{4} - \frac{i}{4}

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Math Problem Analysis

Mathematical Concepts

Complex Numbers
Rationalization
Simplification

Formulas

Multiplication of complex conjugates: (a + bi)(a - bi) = a^2 + b^2
i^2 = -1

Theorems

Properties of Complex Conjugates
Simplification of Fractions

Suitable Grade Level

Grades 10-12