5.2.3. For each of the following quadratic functions, determine whether there is a minimum. If so, find the minimizer and the minimum value for the function. (a) r2-2xy+4y²+x-1, (b) 3r²+3ry+3y2-2x-2y+4, (c) r²+5ry+3y²+21-y, (d) x² + y²+yz+22+x+y-z, (e) r2+ry-s y2-yz+z2-3, (f) r2+5xz+y2-2yz+z2+2r-z-3, (g) r²+ry+y²+yz+z²+zw+w²-22-w.