Giving brainliest! solve for x: 2x + y = 1

For f(x)=2x+1 and g(x)= x^2 -7, find (f•g)(x)

If cos(2x) = tan^2(y), show that cos(2y) = tan^2(x).

The? half-life of a radioactive substance is 20 years. if you start with some amount of this? substance, what fraction will remain in 120 ? years