Question 177417
612) Correct



613) Close, but {{{z^4-16=(z^2+4)(z-2)(z+2)}}}



614) Correct



615) 





{{{25x^2-64=0}}} Start with the given equation



{{{(5x+8)(5x-8)=0}}} Factor the left side (use the difference of squares)




Now set each factor equal to zero:


{{{5x+8=0}}} or  {{{5x-8=0}}} 



{{{x=-8/5}}} or  {{{x=8/5}}}    Now solve for x in each case



So the answers are 


 {{{x=-8/5}}} or  {{{x=8/5}}}