golu23 wrote:1)In the xy plane,at what 2 points does the graph of y(x+a)(x+b) intersect the X axis?
A+B=-1
The graph intersects Y axis AT (0,-6)
2)What is the Avg of 11 conecutive integers
The avg of first nine integers is 7
The avg of last nine integers is 9
Guys i have no idea how to solve these problems.
Problem 1: can be rephrased as
y = (x+a)(x+b)
= x^2 +(a+b)x + ab
Stmt 1: a+b = -1. INSUFFICIENT as ab could be anything, thus changing the roots and hence the points where the graph meets the x axis.
Stmt 2: ab = -6, again a+b could be anything. Hence roots will change. Hence INSUFFICIENT.
Stmt 1 + Stmt 2: gives us a+b and ab thus now there will be unique roots for the equation. SUFFICIENT. Hence
C
Problem 2:
Stmt 1: we know the sum of n numbers in an arithmetic progression is S = (n/2)(2a + (n-1)d), where n = number of terms, a = first term, d = difference between two consecutive terms.
From stmt 1, we know n = 9, S = 7*9, d = 1, hence a can be found hence Sum of 11 terms can be found. SUFFICIENT.
Stmt 2 - we see that again n, d and S are given hence Sum of 11 terms can be found. SUFFICIENT.
Hence
D
