Which statement is true?
a) all waves travel at the same speed through any medium.
b) all waves travel at the same speed if no medium is present.
c) electromagnetic waves require a medium, but mechanical waves do not.
d) mechanical waves require a medium, but electromagnetic waves do not.

D)Mechanical waves require a medium, but electromagnetic waves do not.

Step-by-step explanation:

answer is 67%

step-by-step explanation:

i think it's ф or x=6,-6

step-by-step explanation:

-x^2=-36

x^2=-36

ф

or

if you mean by : -(x^2)=-36

it'll be: x^2=36

x=6,x=-6

hope it'll ! have a good day!

you for asking!