XY Plane
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- Newbie | Next Rank: 10 Posts
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IMO C..
As the equation represents a parabola that intersects x axis twice and y axis once.
the equation from question : y = x(x) + x(a+b)+ab
for it to intersect x axis we need a and b both
so the equation on substituting 0 for y becomes x(x) + (a+b)x +ab=0
this is a quadratic enq with roots -a and -b and can be written as:
x(x) - (-a-b) +ab=0
or
x(x) +x(Sum of roots)+ product of roots=0
1) provides -> sum of roots
2) provides -> product of roots
so answer is C
As the equation represents a parabola that intersects x axis twice and y axis once.
the equation from question : y = x(x) + x(a+b)+ab
for it to intersect x axis we need a and b both
so the equation on substituting 0 for y becomes x(x) + (a+b)x +ab=0
this is a quadratic enq with roots -a and -b and can be written as:
x(x) - (-a-b) +ab=0
or
x(x) +x(Sum of roots)+ product of roots=0
1) provides -> sum of roots
2) provides -> product of roots
so answer is C
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- Newbie | Next Rank: 10 Posts
- Posts: 5
- Joined: Wed Aug 27, 2008 10:05 pm
modification to the earlier post::
the product is -ve so a and b differ in sign
a+b=-1 and ab=-6
=> a=-3 and b=2 or a=2 and b=-3
we get the two points
the product is -ve so a and b differ in sign
a+b=-1 and ab=-6
=> a=-3 and b=2 or a=2 and b=-3
we get the two points