Prove algebraically that the straight line with equation x=2y+10 is a tangent to the circle with the equation x^2+y^2=20

You are a clerk at convenience store. a customer owes 11.69 for a bag of potatoes chips. she gives you a five dollar bill. how much change should the customer receive?

Ineed me i stuck and i don’t want to get it wrong

The input to the function is x and the output is y. write the function such that x can be a vector (use element-by-element operations). a) use the function to calculate y(-1.5) and y(5). b) use the function to make a plot of the function y(x) for -2 ≤ x ≤ 6.