Find the y-coordinate of the vertex:
f(2) = 2^2- 4(2) - 5.

Step-by-step explanation:

f(2)=2²-4(2)-5

f(x)=x²-4x-5

=x²-4x+4-4-5

=(x-2)²-9

vertex is (2,-9)

y co-ordinate of the vertex is -9

system of linear equation

step-by-step explanation:

as given in the data

a= 20 , b= -12

let us suppose that it is a straight line equation

now we know the formula for the system of linear equation

b= ma + c )

here m is slope of a straight line which is equal to formula

m=   (ii)

and here c is a constant

now putting the value of a and b in equation (ii)

m=

m=

putting the value of a,b and m in equation (i) gives us

-12 = + c

-12=-12 + c

adding 12 to both sides

-12 +12 = -12 +12 +c

0 =c

or c=0

as the value of the constant is zero which gives us that it is a linear equation and this order pair satisfies the system of linear equations.