The first five triangular numbers are shown, where n represents the number of dots in the base of the figure, and d(n) represents the total number of dots in the figure.

When n = 1, there is 1 dot. When n = 2, there are 3 dots. When n = 3, there are 6 dots. Notice that the total
number of dots d(n) increases by n each time.

Use induction to prove that
d (n) = n(n+1)/2

Prove the statement is true for n = 1.

the ratio of balloons to tables is 5: 2 and the constant variation is 5.

the equation is y=5x

what do u need to know

step-by-step explanation:

statement #3: proof- ang is congruent to ang ecd : angles are congruent.  

step-by-step explanation:

1: the missing angles in statement #3  

a.) acb  

reason- the reason why the answer is acb is because angle ecd and angle acb are both the same size *that's what the word congruent means this is really simple.  

2: the missing word in reason #3  

c.) vertical  

reason- the reason why the answer is vertical is because the angles in that diagram on figure 2 is slanted, which is vertical, and the e and a both lay on vertical lines. along with the other's, but e and a are the 2 main points you want to focus on. and c is kind of like your starting point, because c is for both angles, not just one.  

i hope that was and understanding.