hw 3.3 problem 3

[Jacob Parker]

For Problem #3  

r= 1/(5s^4) -7/(3s^4)

which math labs says = -4/(5s^5) + 14/(3s^3)

I got -4/(s^5) + 14/(s^3)

My question is why is math labs answer true?

The step before simplification I had (-20s^3)/((5s^4)^2) - (-42s)/((3s^2)^2)

(a^b)^c=a^b*c 

[Jacob Parker]

Never mind I get it (5s^4)^2=25s^8