Question

one root of x2+9x-21=0 is 3 while x2+ 9x+b=0 has equal roots. find b​

Answer 1

Step-by-step explanation:

compare with ax²+bx+c=0

a=1,b=9and c=b

0=b²-4ac

0=9²-4(1×b)

0=81-4(b)

-81=-4(b)

-81/-4=b

81/4=b