(12 x 2) - 5 because twice as many means to multiply by 2. fewer means to subtract.
Given that triangle ABC is right angle triangle. CD is altitude such that AD=BC
ABC is a right angle triangle so apply Pythogorean theorem

(Given that AD = BC)
(Given that AB=3)
...(i)
ADC is a right angle triangle so apply Pythogorean theorem



...(ii)
Plug value (ii) into (i)





Hence final answer is 
Graph each points:
f(x) = -13x + 1
when x = 0, y = 1
f(0) = -13(0) + 1
f(0) = 0 + 1
f(0) = 1
when x = 1, y = -14
f(1) = -13(1) + 1
f(1) = -13 + 1
f(1) = -14
when x = 2, y = -25
f(2) = -13(2) + 1
f(2) = -26 + 1
f(2) = -25
etc.
Graph each point and connect them.
So if you want to add
we distribute
a(b+c)=ab+ac so
-2(m+n-4)=-2m-2n+8
5(-2m+2n)=-10m+10n
n(m+4n-5)=mn+4n^2-5n
so total we ahve
-2m-2n+8-10m+10n+mn+4n^2-5n
group like terms
4n^2+-2m-10m-2n+10n-5n+mn+8
add like temrs
4n^2-12m+3n+mn+8