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secondary 3 | A Maths
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somebody please explain why b has to be a negative number ? I know why a has to be positive but idk why b has to negative ? Like why can’t c be negative? sorry i just keep getting these questions wrong and I really need a detailed explanation as to why the values are the way they are
Date Posted: 2 years ago
Views: 712
normally, for a quadratic curve to be completely above the x-axis, just need 2 conditions ...
a>0 and b^2-4ac<0.
for this question, there is additional condition abc<0.
since a is positive, then if c is negative,
will lead to b^2-4ac will always be positive.
so c must be positive.
since a & c are both positive, then for abc<0,
need b to be negative.
therefore, need ...
a>0
b<0
c>0
and b^2<4ac
just need to give a simple set of numbers that satisfy these 4 conditions, eg, a = 1, b= -1, c = 1.
a>0 and b^2-4ac<0.
for this question, there is additional condition abc<0.
since a is positive, then if c is negative,
will lead to b^2-4ac will always be positive.
so c must be positive.
since a & c are both positive, then for abc<0,
need b to be negative.
therefore, need ...
a>0
b<0
c>0
and b^2<4ac
just need to give a simple set of numbers that satisfy these 4 conditions, eg, a = 1, b= -1, c = 1.
See 1 Answer
done
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clear
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i hope this is clear enough! Let me know if you need further clarifications
Date Posted:
2 years ago
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