Question

verify by substitution that the given function is a solution of the given differential eq.
y"+4y=0; y1 =cos2x,y2 =sin2x

Answer 1

\[\Large\rm y''+4y=0\]

\[\Large\rm y_1=\cos2x\]\[\Large\rm y_1'=-2\sin2x\]\[\Large\rm y_1''=-4\cos2x\]So what do you get when you plug in your y1 and derivatives? :)\[\Large\rm y_1''+4y_1=?\]

Answer 2

-4cos2x +4cos2x =0! aha!

Answer 3

ahh you are awesome! that helps a lot

Answer 4

cool c: