For the first question:
We know that PQR + PRQ + QPR = 180 (sum of the angles of the smaller triangle.
We also know that PRS + PRQ = 180 (sum of the angles that form a straight line.
We are asked to solve for PRS - PQR
1) QPR = 30
So PQR + PRQ = 150
and PRQ + PRS = 180
so we can combined those equations and find that PQR = PRS - 30 so we know the difference in the two angles. therefore 1 is sufficient.
2) is telling us exactly the same thing that 1) is (by telling us that the other two angles of the small triangle = 150, then we know that the third angle = 30, just like 1) told us. So, if 1 is suff, then 2 is suff.
Answer is D.
For the second question:
y = (x+a) (x+b)
y = x^2 +xa + xb + ab
y = x^2 + x(a+b) + ab
So, to solve (and therefore graph) this equation, we need to know (a+b) and ab.
1) tells us what (a+b) is but doesn't give us any information about ab so insuff.
2) we know that then x = 0, y = -6. If we plug that into the equation, then:
-6 = 0^2 + x(a+b) +ab
-6 = 0 + 0 +ab
-6 = ab
only tells us about ab, not (a+b), so insuff
together, they tell us (a+b) and ab, so we can solve the equation and figure out the points where x is 0.
Answer is C
Too tired to tackle question 3.
-Carrie
