Is the lines y=-x-7 and y-x=20 perpendicular?

yes

Step-by-step explanation:

rearrange the equations

x+y+7=0 &

x-y+20=0

find out slopes of the lines

which is -a/b

for the first one it is

-1/1=-1

and for the second

-1/-1=1

find the product of the slopes

-1×1 = -1

since the product of the slopes is -1

the lines are perpendicular

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step-by-step explanation:

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step-by-step explanatio89