We will begin by working through Part (a): Simplify √18
To simplify a square root such as the one above, we must factor out perfect square numbers (this means we must find a number that multiplies to 18 and gives a whole number when we square root it). Using our knowledge that √9 is a perfect square, we should factor out a 9 from 18, as modeled below:
√18 = √(9*2)
We can separate this square root into two square roots multiplied together, as shown below:
√(9*2) = √9 * √2
Now, we should simplify √9, which equals 3, because 3 * 3 = 9.
√9 * √2 = 3 * √2 = 3√2
Therefore, √18 = 3√2.
Now, we can move on to the next problem: √6 * √15.
To begin this problem, we can multiply the square roots together, which means multiplying the numbers under the radical.
√6 * √15 = √(6*15) = √90
To simplify this, we use the same process as above:
√90 = √(10 * 9) = √9 * √10 = 3√10
Note: We know that this fully simplified because we cannot factor out another perfect square number from the number under the radical (10).
Therefore, your two answers are 3√2 and 3√10.
Hope this helps!
Given is square root of a negative real number, i.e. 
When we find square root of positive real numbers, we get Real answers.
But when we find square root of negative real numbers, we get Imaginary answers. To solve them, we can split the given negative number into product of -1 and the number itself but with positive sign. e.g. -4 = -1 x 4.
For square root of -1, we use english letter 'i' called Imaginary unit i.e. 
Now we can use -0.25 = -1 x 0.25
Hence, "0.5i" is the final answer.
The bottom right.
The line best fit is usually the line that follows the trend of dots in the scatter plot. In the other 3, you can tell that there seems to be no trend between either the line or the dots.
The bottom right one has a line pretty much right through the middle of the scattered dots and follows the trend.
500 + 30g <span>≤ 8000
30g </span><span>≤ 7500
g </span><span>≤ 250</span>
Unit rate = total buttons/ total controllers
Unit rate = 26/2 = 13
Unit rate: 13 buttons per controller
