So we know that our equation is: X2 - 10X +17 = 0. STEP 1: rearrange this equation to get x on one side: X2 - 10X = -17. Lets call this, "equation 1". STEP 2: Understand that (X + a)2 = X2 + 2aX + a2. Comparing the terms with equation 1, we can see that 2aX = -10 meaning that a = -5. STEP 3: Understand that (X - 5)2 = X2 - 10X +25. STEP 4: Rearranging the equation to match the left hand side of equation 1 gives: X2 - 10X = (X - 5)2 - 25. STEP 5: substituting that into equation 1 gives: (X - 5)2 - 25 = -17 Therefore, (X - 5)2 - 8 = 0 . Hence, a = -5 & b= -8