On this necklace the ratio of black beads to white beads is 1:4 How many more black beads do you need to add to make the ratio of black to white 4:1 ? WILL GIVE BRAINLIEST!!!

Which sum or difference identity would you use to verify that cos (180° - q) = -cos q? a.) sin (a -b) = sin a cos b – cos a sin b b.) cos (a -b) = cos a cos b – sin a sin b c.) cos (a -b) = cos a cosb + sin a sin b d.) sin (a + b) = sin a cos b + cos a sin b