Step 1 : Find the sum of (3a2−2a+5) and (a2−5a−7) Sum of (3a2−2a+5) and (a2−5a−7) =(3a2−2a+5)+(a2−5a−7) =3a2+a2−2a−5a+5−7
=4a2−7a−2 ….(1)
Step 2 : Find the sum of (5a2−9a+3) and (2a−a2−1) Sum of (5a2−9a+3) and (2a−a2−1) =5a2−9a+3+2a−a2−1 =5a2−a2−9a+2a+3−1
=4a2−7a+2 …..(2)
Step 3: Find the required diffrence (4a2−7a+2)−(4a2−7a−2) =4a2−7a+2−4a2+7a+2 =4a2−4a2−7a+7a+2+2
= 4
Hence, the required difference is 4.