Ask Singapore Homework?

Upload a photo of a Singapore homework and someone will email you the solution for free.



Question

secondary 4 | E Maths
One Answer Below

Anyone can contribute an answer, even non-tutors.

Answer This Question
Jason
Jason

secondary 4 chevron_right E Maths chevron_right Singapore

Bmat ques. How do I know if two line intercepts just by looking at equation

Date Posted: 5 years ago
Views: 249
Eric Nicholas K
Eric Nicholas K
5 years ago
The easiest is sketching of all graphs including intercept values. Simultaneous solving is not recommended.
J
J
5 years ago
Depends on how well your visualisation of the graphs are.

For 2 and 3, they are quadratic curves centred at the y axis. 2 is u shaped with the minimum at y = 0, x = 0 , while 3 is n shaped with maximum point at x = 0, y = 1. They will 'overlap' and intersect at 2 points

4 is a straight line with y intercept of 6. Beyond the y intercept, y increases/decreases linearly with x. 4 would cut graph 2 at 2 points since graph 2 is going upward as x moves away from 0.

This is the same for 1 and 3, where 1's y intercept is -2 and below the x axis. So it would cut graph 3 at 2 points since graph 3 is moving downwards as x moves away from 0.
J
J
5 years ago
The slightly trickier one is option A. But that is easily solved if you equate the graphs, giving a result of x = 2 and x = 1.

It is actually quite intuitive that option E is the answer since the quadratic graph 3 is below the x axis pointing downwards ,and the linear graph 4 is much higher, with its intercept 6 units above the x axis, which suggests they are unlikely to meet.


I would say simultaneous equations should be done if you want to be absolutely sure.

And the ones given in the question are actually quite simple and can be done mentally, to determine if there are real roots or not. Complete the square if necessary (You can also check the discriminant)

To me this is much faster than drawing graphs. For graphs you will have to consider the scale to use. And you are unlikely to have graph paper for such MCQs so your drawing has to be accurate and to scale, if not it may result in an incorrect interpretation.

See 1 Answer

done {{ upvoteCount }} Upvotes
clear {{ downvoteCount * -1 }} Downvotes
syjiaxuan
Syjiaxuan's answer
290 answers (A Helpful Person)
1st
Hope this helps, ans is E I think
Eric Nicholas K
Eric Nicholas K
5 years ago
The first two graphs barely intersect at one point.

The third and fourth graphs are just way too far apart for intersection.