Question

What is the sum of √-2 and √-18?


A) 4√2
B) 4√2i
C) 5√2
D) 5√2i

Answer 1

Answer: OPTION B

Explanation:

First of all, you need to know the concept of imaginary number or i.

i (imaginary number)= √-1 ⇔ In real number world, √-1 will be undefined,

and thus this is called imaginary number

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√-2=√2 × √-1

• √2=√2
• √-1= i

√-2=√2× √-1

√-2=√2 × i

√-2= √2 i

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√-18=√9 × √2 × √-1

• √9=3 ⇒ This is a perfect square
• √2=√2
• √-1=i

√-18= √9 × √2 × √-1

√-18= 3 × √2 × i

√-18= 3√2 i

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Addition in radical numbers is as usual as normal number. HOWEVER, only numbers that has the same radical (i.e 2√3 and 7√3) can combine.

√-2 + √-18

=√2 i + 3√2 i

=4√2 i

Hope this helps!! :)

Please let me know if you have any question