+0  
 
0
85
1
avatar

If the two roots of the quadratic 4x^2 + 7x + k are (-7 +/- i*sqrt(79))/8, what is k?

 Jun 21, 2022

Best Answer 

 #1
avatar+2448 
0

By the quadratic formula, the roots are: \(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\).

 

Substituting what we know, we have: \(x = {-7 \pm \sqrt{49-16c} \over 8}\)

 

This means that the discriminate must equal -79, giving us the equation: \(49 - 16c = -79\)

 

Subtracting 49 from both sides, we have: \(-16c = -128\), meaning \(k = \color{brown}\boxed{8}\)

 Jun 21, 2022
 #1
avatar+2448 
0
Best Answer

By the quadratic formula, the roots are: \(x = {-b \pm \sqrt{b^2-4ac} \over 2a}\).

 

Substituting what we know, we have: \(x = {-7 \pm \sqrt{49-16c} \over 8}\)

 

This means that the discriminate must equal -79, giving us the equation: \(49 - 16c = -79\)

 

Subtracting 49 from both sides, we have: \(-16c = -128\), meaning \(k = \color{brown}\boxed{8}\)

BuilderBoi Jun 21, 2022

4 Online Users

avatar