To get the vertex of the parabola we proceed as follows;
y=-7(x-4)^2-5
The above can be written as:
y=-7x^2+56x-117
The values of a,b and c are:
a=-7, b=56 and c=-117
x=-b/(2a)
x=-56/(-7*2)=4
but;
y=-7x^2+56x-117
y=-7(4)^2+56(4)-117
y=-5
Thus;
x=4 and y=-5
The vertex will be at point (4,-5)
Given:
y is proportional to x.
y=10 and x=8.
To find:
The constant of proportionality and the equation for the proportional relationship.
Solution:
y is proportional to x.
...(i)
Where, k is the constant of proportionality.
Putting y=10 and x=8, we get
Putting 
in (i), we get
Therefore, the contestant of proportionality is and the equation for the proportional relationship is .
The statement given is :
If a figure has three sides , it is a triangle
contrapositive statement is :
If a figure is not a triangle, then it does not have three sides.
last option is correct
