7. -8/3
8. 4/35
9. -21/50
10. 35/64
11.-25/54
I'm not sure how to write the rule, but every time you add one more to the sum of the last two. First, you add 1, then 2, then 3. 1+1=2 2+2=4 4+3=7 7+4=11 and so on. I hope this helps!
This is the concept of algebra, to solve the expression we proceed as follows;
cos 2x-cosx=0
cos 2x=cosx
but:
cos 2x+1=2(cos^2x)
thereore;
from:
cos 2x=cos x
adding 1 on both sides we get:
cos 2x+1=cos x+1
2(cos^2x)=cosx+1
suppose;
cos x=a
thus;
2a^2=a+1
a^2-1/2a-1/2=0
solving the above quadratic we get:
a=-0.5 and a=1
when a=-0.5
cosx=-0.5
x=120=2/3π
when x=1
cos x=1
x=0
the answer is:
x=0 or x=2/3π
