In Exercises 3-6, solve the systems of equations using Gaussian elimination. (a) Perform the back substitution using equations. (b) Perform the back substitution using matrices. X1 + Xz + X3 = 6X1 - Xz + X3 = 2x1 + 2x2 + 3x3 = 14

9/21/16 ● To show a limit doesn’t exist ○ All #’s can’t exist ■ Prove that left and righthand limits don’t exist or are not equal ■ Or one or both go to infinity ■ One or both onesided limits do not exist Challenge problems 1. Prove lim (x>a) ax^2 + Bx + y = aa^2 + Ba + y 2. Prove that lim (x>0) lim sin (pi/x) does not exist ● Squueze theorem ○ If lim (x>a) f(x) = lim (x>a) g(x) = L and for x near but not equal to a f(x) a) h(x) = L ■ EXAMPLE ● h(x) = x sin x ● What is lim (x>0) h(x) ● 1