Answer:
i think 4 is b
Step-by-step explanation:
It makes and obtuse right triangle.
Get x on one side then you can use substitution
So, change x+3y=3 to x= -3y+3
Then plug in x to other equation to find y
2(-3y +3)-3y=-12
-6y + 6 -3y = -12
-9y = -18
Divide both sides by negative nine to find y
y = 2
Then plug in to original equation to find x
x + 3(2) = 3
x + 6 = 3
x = -3
So, y = 2 and x = -3
S = a*((1 - r^(n+1))/(1-r))
S = 1*((1 - 2^(7+1))/(1-2))
S = 1*((1 - 2^8)/(1-2))
S = 1*((1 - 256)/(1-2))
S = 1*((-255)/(-1))
S = 255
So 1+2+4+8+...+128 = 255
