Question

find the values of K for which the equation9x²+2Kx+1=0 has real roots

Answer 1

$<b><font face=copper black size=4 color=red>$

a = 9 , b = 2k, c = 1
$<b><font face=copper black size=4 color=blue>$

D = b2-4ac
$<b><font face=copper black size=4 color=green>$

0 = (2k)2-4*9*1
$<b><font face=copper black size=4 color=blue>$

0 = 4k2-36
$<b><font face=copper black size=4 color=violet>$

36 = 4k2
$<b><font face=copper black size=4 color=red>$

36/4 = k2
$<b><font face=copper black size=4 color=blue>$

k = √ 9 = 3