Posted by **lisa** on Thursday, April 5, 2012 at 10:07pm.

If 4x^2+9=kx, what value of k will produce equal roots?

the answer is 12 but i don't understand how you get it, please help!

- alg2/trig -
**Bosnian**, Thursday, April 5, 2012 at 10:30pm
4 x ^ 2 + 9 = kx

4 x ^ 2 - k x + 9 = 0

Quadratic equation has two real roots, if Discrininant Ä = 0

Ä = b ^ 2 - 4 * a * c

In this case :

a = 4

b = - k

c = 9

Ä = b ^ 2 - 4 * a * c

Ä = ( - k ) ^ 2 - 4 * ( 4 ) * 9

Ä = k ^ 2 - 144 = 0

k ^ 2 - 144 = 0

k ^ 2 = 144

k = sqrt ( 144 )

k = ± 12

For k = - 12

4 x ^ 2 + 9 = k x

not equal becouse left side of equation are positive ( 4 x ^ 2 + 9 ) are allways great of 0 ) ,and right side of equation are negative.

So solution are k = 12

- alg2/trig -
**Bosnian**, Thursday, April 5, 2012 at 10:32pm
Quadratic equation has two real equals roots, if Discrininant Ä = 0

Ä = greek letter Delta

## Answer This Question

## Related Questions

- alg2\trig - if a3= 17 & a8=37 are terms in annarithmetic sequece, fina a1 & d. ...
- alg2/trig - what is the smallest value of k that would make the roots of the ...
- Algebra problems - I have some problems that I would like checked please. Find ...
- maths - q1) 2cos2x is f(x) -square root3 is g(x) solve f(x)-g(x)=0 to get points...
- algebra2/trig - for what are value of k are the roots of 3x^2-6x+k=0 equal?
- Math - determine the value(s) of k which a quadratic equation x^2+kx+9=0 will ...
- Trig - Determine the roots of the function f(x)=-2cos(3x)-1. Can you please show...
- Pre-Calculus/Trig Check please and help - Could someone please check the first ...
- alg2/trig - The expression a/a-b + b/b-a is equivalent to a) 1 b)-1 c) ab/a-b d)...
- Algebra-help please - I already asked this question once about the absolute ...

More Related Questions