Answer:
x=25
Step-by-step explanation:
x+5+6x=180
7x+5=180
7x=175
x=25
There are two ways to work this out: normal variables or using "imaginary" numbers.
Normal variables:
![(7+2i)(3-i)\\(7*3)+[7*(-i)]+(3*2i)+[2i*(-i)]\\21-7i+6i-2i^{2}\\\\21-i-2i^{2}](https://tex.z-dn.net/?f=%20%287%2B2i%29%283-i%29%5C%5C%287%2A3%29%2B%5B7%2A%28-i%29%5D%2B%283%2A2i%29%2B%5B2i%2A%28-i%29%5D%5C%5C21-7i%2B6i-2i%5E%7B2%7D%5C%5C%5C%5C21-i-2i%5E%7B2%7D)
Imaginary numbers:
Using the result from earlier:

Now since

, then the expression becomes:
Step-by-step explanation:
1st term = -n²+6
= -(1)²+6
= -1+6
=5
2nd term = -(2)²+6
= -4+6 = 2
3rd term= -(3)²+6
=-9+6 = -3
4th term= -(4)²+6
= -16+6 = -10
5th term = -(5)²+6 = -25+6 = -19
6th term = -(6)²+6 = -36+6 = -30
5,2, -3,-10,-19, -30
optionB
(x^2 +5x+2.5^2) +4+5
(x+2.5)^2+9
vertex -2.5,9