Question

If one root of quadratic eqa 2x square + kx -6=0 is 2, find the value of k and find other root <br />

Answer 1

Substitute x=2in quadratic equation
$2 {x}^{2} + kx - 6 = 0$
=>
$2 {(2)}^{2} + k(2) = 6$
=> 2k=6-8= -2 => k= -1 . substitute k=-1 again in the quadratic equation
$2 {x}^{2} + ( - 1)x - 6 = 0$
=>
$2 {x}^{2} - 4x + 3x - 6 = 0$
=>
$2x(x - 2) + 3(x - 2) = 0$
=>
$(2x + 3)(x - 2) = 0$
=> x=2 and -3/2. so other root of the quadratic equation is x= -3/2 and k=-1 .Hope it helps you...

Answer 2

Substitute x=2in quadratic equation 
2 {x}^{2} + kx - 6 = 02x2+kx−6=0 
=>
2 {(2)}^{2} + k(2) = 62(2)2+k(2)=6 
=> 2k=6-8= -2 => k= -1 . substitute k=-1 again in the quadratic equation 
2 {x}^{2} + ( - 1)x - 6 = 02x2+(−1)x−6=0 
=> 
2 {x}^{2} - 4x + 3x - 6 = 02x2−4x+3x−6=0 
=>
2x(x - 2) + 3(x - 2) = 02x(x−2)+3(x−2)=0 
=>
(2x + 3)(x - 2) = 0(2x+3)(x−2)=0 
=> x=2 and -3/2. so other root of the quadratic equation is x= -3/2 and k=-1 .Hope it helps you...