In Diagram 2, O is the origin. Straight line PQ is parallel to straignt line RS and straight line QR is parallel to y-axis.
The equation of the straight line PQ is y= 2x + 5.

a) state the equation of the straight line QR.
ans: Q(1,7) , x=1

Can someone explain to me how to get the answer?

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.