Eric Nicholas K's answer to Rella's Secondary 3 A Maths Singapore question.
done
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clear
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Logical reasoning is needed at the last part.
Date Posted:
4 years ago
So what is the final answer
We need to show that b2 - 4ac > 0 in this question.
It’s a ‘show that’ question.
Once you obtain b2 - 4ac = q (5q - 4), you need to explain why that product is positive when q is negative. Once you have done so, you can conclude by saying that b2 - 4ac > 0 when q is negative, and this translates to having two real and distinct roots.
It’s a ‘show that’ question.
Once you obtain b2 - 4ac = q (5q - 4), you need to explain why that product is positive when q is negative. Once you have done so, you can conclude by saying that b2 - 4ac > 0 when q is negative, and this translates to having two real and distinct roots.
As a side note, in ‘show that’ questions such as this one, we cannot start by immediately saying that b2 - 4ac > 0; in other words, you must not write the ‘> 0’ while attempting to prove that it is indeed > 0.
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