Write the complex number in standard form.
$\sqrt { - 20 } \times \sqrt { - 18 }$

A) $6 \sqrt { 10 }$
B) $- \sqrt { 20 }$
C) - $6 \sqrt { 10 }$
D) $\sqrt { 18 }$
E) $\sqrt { 20 }$

Question

Write the complex number in standard form. 
$\sqrt { - 20 } \times \sqrt { - 18 }$  
 
A) $6 \sqrt { 10 }$
B) $- \sqrt { 20 }$
C) - $6 \sqrt { 10 }$
D) $\sqrt { 18 }$
E) $\sqrt { 20 }$

Quizplus · Accepted Answer

The product of two complex numbers $\sqrt{-20}$ and $\sqrt{-18}$ can be simplified by first expressing each under the square root as a product of their prime factors and using the property of imaginary numbers $i^2 = -1$. Thus, $\sqrt{-20} = \sqrt{20}i = \sqrt{4*5}i = 2\sqrt{5}i$ and $\sqrt{-18} = \sqrt{18}i = \sqrt{9*2}i = 3\sqrt{2}i$. Multiplying these gives $2\sqrt{5}i * 3\sqrt{2}i = 6\sqrt{10}i^2$. Since $i^2 = -1$, the result is $-6\sqrt{10}$, which is in standard form.

Write the Complex Number in Standard Form −20×−18\sqrt { - 20 } \times \sqrt { - 18 }−20​×−18​

Write the Complex Number in Standard Form $\sqrt { - 20 } \times \sqrt { - 18 }$