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Find the roots of x^2+7x+12=0...

Find the roots of `x^2+7x+12=0`

A

exactly two real root

B

exactly one real root

C

exactly four real roots

D

infinite number of real roots

Text Solution

Verified by Experts

The correct Answer is:
D
Lert `e^(sin x)=t`
Then lie given equation can be written as
`t-1/t-4=0impliest^(2)-4t-1=0`
`:.t=(4+sqrt((16+4)))/2`
`impliese^(sinx)=(2+sqrt(5))[ :' e^(sinx)gt0,:` taking `+ve` sign]
`impliessinx=log_(e)(2+sqrt(5))`………….ii
`:'(2+sqrt(5))gte[:' e=2.71828]`
`implieslog_(e)(2+sqrt(5))gt1` ............iii
From eq. ii and iii we get
`sin x gt1` [ which is impossible]`
Hence no real root exists.
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