+0

Help. ​

0
318
6
+4676

Help.

Nov 2, 2017

#1
+98197
+2

12x^2 - 11x  = 11

12x^2 - 11x - 11 = 0      ⇒  ax^2 + bx  + c  = 0

The discriminant is     b^2  - 4ac

(-11) ^2  - 4(12)(-11)  =  121 + 528  >  0

So.....when the discriminant > 0....we will have two REAL solutions

Nov 3, 2017
#2
+98197
+1

Mmmmm...on the second one....the discriminant > 0...but I don't see how that decides much of anything

I just means that we have real roots

Look at this graph :  https://www.desmos.com/calculator/iohx6ebf5u

The curve definitely exceeds 141 for a long period of time   !!!!

Nov 3, 2017
#3
+4676
0

NotSoSmart  Nov 3, 2017
#4
+98197
+1

Yep   .....

Nov 3, 2017
#5
+4676
+1

Ok, thanks

NotSoSmart  Nov 3, 2017
#6
-1

For T to be greater than 141, you need -0.005x^2 + 0.45x to be greater than 16, so the quadratic that you should be considering is -0.005x^2 + 0.45x - 16 = 0.

If this has two real roots, between these two values of x, T will be greater than 141, otherwise T will never reach 141.

It doesn't, so it doesn't.

(Chris has typed in 0.0005 rather than 0.005).

Tiggsy

Nov 3, 2017