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Mathematics 20 Online
OpenStudy (anonymous):

3.Find the range of values of x of each of the following. @ganeshie8

OpenStudy (anonymous):

a)\[12>x(x-4)\] b)\[x(7-5x)>2\]

OpenStudy (anonymous):

a)\[x^2-4x-12>o\]

ganeshie8 (ganeshie8):

careful about the inequality

OpenStudy (anonymous):

\[(x-6)(x+2)>0\]

ganeshie8 (ganeshie8):

hold up

ganeshie8 (ganeshie8):

\[12>x(x-4)\] subtracting 12 gives \[0 >x(x-4)-12\] yes ?

OpenStudy (anonymous):

yep

ganeshie8 (ganeshie8):

go to right side of that and look at it

ganeshie8 (ganeshie8):

\[\large x(x-4)-12 \color{red}{<} 0\]

ganeshie8 (ganeshie8):

\[\large x^2-4x-12 \color{red}{<} 0\]

ganeshie8 (ganeshie8):

\[\large (x-6)(x+2) \color{red}{<} 0\]

ganeshie8 (ganeshie8):

now think of how the graph of parabola with intercepts 6 and -2 looks like

OpenStudy (anonymous):

opens upward

ganeshie8 (ganeshie8):

yes! draw a rough sketch

OpenStudy (anonymous):

|dw:1420358166381:dw|

ganeshie8 (ganeshie8):

|dw:1420358214238:dw|

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