I need help with Geometry

The equation x2 – 1x – 90 = 0 has solutions {a, b}. what is a + b?

Brainlest answer can you find the area and circumference of a circle given the radius or diameter? if its yes or no explain why

Colby and jaquan are growing bacteria in an experiment in a laboratory. colby starts with 50 bacteria in his culture and the number of bacteria doubles every 2 hours. jaquan starts with 80 of a different type of bacteria that doubles every 3 hours. let x equal number of days. colbys experiment follows the model: a.) y=50*2^x b.) y=50*2^8x c.) y=50*2^12x jaquans experiment follows the model: a.)80*2^x b.)80*2^8x c.)80*2^12x