9. If a, b, c are 3 consecutive integers, prove that (ai) (a + i) (c+i) (c i)= b + 1. 4 10. If f(x)=4x, find f(x+1)-f(x) in terms of f(x). 2 11. Three numbers are in AP. Another 3 numbers are in GP. The sum of first term of the AP and the first term of the GP is 85, the sum of second term of AP and the second term of the GP is 76 and that of the 3rd term of AP and 3rd term of GP is 84. The sum of the AP is 126. Find each term of AP and GP. 12. Find the number of subsets of a set A containing 10 elements. 1 4 13. In a survey of 700 students in a medical college 200 went for regular entrance coaching, 295 attended only correspondence coaching, 115 attended both regular and correspondence coaching. Find how many got admission without any entrance coaching.