People buy me to eat, but never eat me. What am I?

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

How do you determine whether a relationship represented as as graph is linear or nonlinear

Ascientist has 50 grams of a radioactive element. the amount of radioactive element remaining after t days can be determined using the equation (1) after two days the scientist receives a second shipment of 50 grams of the same element. the equation used to represent the amount of shipment 2 remaining after t days is 10) - 50 which of the following is an equivalent form of the expression for the amount remaining in shipment 2? what’s the answer?