Points: 0.5/ of 1 Solve the following difference equations. K (a) yn = -0.4yn -1 +21, yo = 24 (b) yn = yn-1 -4, yo = 5 (a) To solve the difference equation, yn = ayn - 1 + b, a # 1, what formula should be used? b b yn +(yo a 1 - a 1 - a b Evaluate 1- a where a is the coefficient of the y - , term and b is the constant term in y, = -0.4y -1 + 21. b 15 1 - a (Simplify your answer.) Substitute the values of a, b - a and yo into the formula and simplify. yn = 1 - a yo = 15 + (24 -15)( -0.4)" = (Use integers or decimals for any numbers in the expression. Do not factor.)