Which set of side lengths forms a right triangle
2, 3 , 13
4, 6, 10
9, 12, 18
15, 36, 39

Step-by-step explanation:

First let us apply triangle inequality to check whether these sides form a triangle at all

2+3 <13 hence 2,3,13 cannot form a triangle

4,6,10 L 4+6 =10 hence a straight line but not a triangle

Next

9,12,18

These three can form a triangle.

To check right angle:

18^2 =324  :  9^2+12^2 =81+144 =225

Pythagorean not satisfied hence not right triangle

15,36,39

These form a triangle.

39^2 = 1521

15^2+36^2 =225+1296=1521

Yes.  Hypotenuse square = sum of squares of legs

Hence 15,36,39 forms a right triangle.

x = -3

y = -18

step-by-step explanation:

to solve by substitution, substitute one variable and solve for the other. then substitute again to find the remaining variable.

x-1/3(3x-9) = -3 since y=3x-9 substittute y.

x-1/3(3x-9)=-3

x + x +3 = -3

2x+3=-3

2x+3-3= -3-3

2x=-6

x=-3

substitute again into y=3x-9

y=3(-3)-9

y=-9-9

y=-18

addition

step-by-step explanation: