Solve it using elimination method of simultaneous 2x²+y²=19 and x+3y=0

Which approach to the theory-and-research cycle does the following sequence reflect: (1) specific observations suggest generalizations, (2) generalizations produce a tentative theory, (3) the theory is tested through the formation of hypotheses, and (4) hypotheses may provide suggestions for additional observations?

Evaluate the expression for the given value of the variable 2×(c2-5) for c=4

The sum of the reciprocal of a positive number and the reciprocal of 2 more than the number is 3/4 equation: the number is