Which equation is the inverse of y=100-x2

Adepartment store purchases screen-printed t-shirts at a cost of $5 per shirt. they mark up the price 150% (making the selling price 250% of the store's purchase price) and put them on the sales floor. every month that a t-shirt doesn't sell, the store reduces the selling price by 25%.

Solve for x and y: 217x + 131y = 913; 131x + 217y = 827

Consider the input and output values for f(x) = 2x - 3 and g(x) = 2x + 7. what is a reasonable explanation for different rules with different input values producing the same sequence?