If x∆y = 3x - y², then
5∆1 = 3×5 - 1² = 15 - 1 = 14
and
14∆6 = 3×14 - 6² = 42 - 36 = 6
So (5∆1)∆6 = 6.
Given:
The number is
.
To find:
The a+bi form of given number.
Solution:
We have,

It can be written as

![[\because \sqrt{ab}=\sqrt{a}\sqrt{b}]](https://tex.z-dn.net/?f=%5B%5Cbecause%20%5Csqrt%7Bab%7D%3D%5Csqrt%7Ba%7D%5Csqrt%7Bb%7D%5D)
![[\because \sqrt{-1}=i]](https://tex.z-dn.net/?f=%5B%5Cbecause%20%5Csqrt%7B-1%7D%3Di%5D)

Here, real part is missing. So, it can be taken as 0.

So, a = 0 and
.
Therefore, the a+bi form of given number is
.
Answer: 5
Step-by-step explanation:
There are 15 years was his money invested.
<h3>
What is simple interset?</h3>
Simple Interest is an easy method of calculating the interest for a loan/principal amount.
Given
Frank invests $1,000 in simple interest investment account that pays 8% a year.
After a number of years, he withdraws his balance of $2,200.
The number of years was his money inversted is;

Where p is the principal amount, r is the rate of interest, I is the amount and t is the time.
Substitute all the values in the formula;

Hence, in the 15 years was his money invested.
To know more about investing click the link given below.
brainly.com/question/26677076