(x-6)(x+7) > 0
use a coordinate lane
|dw:1418409031122:dw|
do you understand the sings I put on the lane
or you could just solve x>6 x>-7
you need values of x, where there stands + on line. so it will be x<-7 and x>6
isnt it the other way x>-7
your subtracting, not dividing or multiplying so the signs dont switch
you must have mistaken, for example x=0 and the product won't be bigger than 0
you need values of x where factors are both - or both +
x-6=0 x=-6 x+7=0 x=-7 \[\left( x-a \right)\left( x-b \right)>0\] means x does not lie between a and b. \[\left( x-a \right)\left( x-b \right)<0\] means x lies between a and b
but when solving for an equation, you get each parenthesis and = it to 0. so isn't it x-6>0 and x+7>0
the @surjithayer is correct. I didn't think of that method.
step by step solution attached below
one more method \[\left( x-6 \right)\left( x+7 \right)>0\] \[x^2+x-42>0\] adding 42 to both sides \[x^2+x>42\] \[adding~both~sides~\left( \frac{ co-efficient~of~x }{ 2 } \right)^2~i.e.,\left( \frac{ 1 }{ 2 } \right)^2~or~\frac{ 1 }{ 4 }\] \[x^2+x+\frac{ 1 }{ 4 }>42+\frac{ 1 }{ 4 }\] \[\left( x+\frac{ 1 }{ 2 } \right)^2>\frac{ 168+1 }{ 4 }\] \[\left( x+\frac{ 1 }{ 2 } \right)^2>\left( \frac{ 13 }{ 2 } \right)^2\] \[\left| x+\frac{ 1 }{ 2 } \right|>\frac{ 13 }{ 2 }\] \[\left| x+a \right|>b~\rightarrow~x+a <-b~and~x+a >b\] complete it.
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