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The value of `b`for which the equation `2(log)_(1/(25))(b x+28)=-(log)_5(12-4x-x^2)`has coincident roots is`b=-12`(b) `b=4orb=-12``b=4orb=-12`(d)`b=-4orb=12` |
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Answer» LHS `2log_(1/25)(bx+28)2log_(5^(-2))(bx+28)` LHS `(2/-2)log_5(bx+28)=-log_5(bx+28)` `log_5(bx+28)=-log_5(12-4x-x^2)` `log_a^x=log_a^y` `x=y` `bx+28=12-4x-x^2` `x^2+4x+bx+28-12=0` `x^2+(4+b)x+16=0` `(4+b)^2-4*16=0` `16+b^2+8b-64=0` `b^2+8b-48=0` `(b+12)(b-4)=0` `b=4,-12`. |
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