When solving a system of equations by substitution, what is meant by a useless result ((12 = 12))?

Find the center and the radius of the circle with the equation: x^2-2x+y^2+4y+1=0?

What is the value of the expression i 0 × i 1 × i 2 × i 3 × i 4? 1 –1 i –i

How many heads would you expect if you flipped a coin twice? first, fill in the table below with the correct probabilities. hint: the sample space for flipping a coin twice is {hh, ht, th, tt}. a = b = c = f