H2 maths (inequality)

TenSaru SG

How do you solve 2^(m-3)+20m>390 ?

If I must use graphic calculator how do I use it?

Thanks in advance! =)

eagle SG

yes use graphic calculators

You can plot 2^(m-3)+20m - 390

Then find the x-intercepts... and the inequalities in which the above is greater than zero

wee_ws SG

Hi,

Follow these steps if you are using TI graphic calculator:

1. Press 'Y='.

2. Type '2^(X-3)' for Y1.

3. Type '390-20X' for Y2.

4. Press 'ZOOM 0'. You do not have an intersection between two graphs yet.

5. Press 'WINDOW' and enter '15' for 'Xmax', so that you could obtain an intersection between two graphs.

6. Press 'GRAPH', to view the intersection.

7. Press '2ND TRACE'. Select '5'.

8. Press 'ENTER' three times. GC gives a value of X = 10.492978.

Since the exponential curve is to be higher than the straight line, we take the solution to be x > 10.5, correct to 3 significance figures.

Try to get accustomed to the GC steps, because it is often the case that schools ask students to do independent self-study in their bid to 'teach less, learn more'.

Thanks!

Cheers,
Wen Shih

The Showstopper SG

Hi,