In finding intersections for quadratic curves
what is the answer to: y=x2-2x-35
I could tell you the answer but that wouldn't be
much fun would it? Do you have access to spreadsheet software? you
could try this ... Put minus 10 in cell A2 and go down column A
increasing by one each row until you get to plus 10 (that is -10,
-9, -8 ... 8, 9, 10) in cell B2 type =A2*A2 this is your X2 in cell
C2 type =A2*(-2) this is your -2X in cell D2 type -35 this is your
minus 35 in cell E2 type =sum(B2..D2) now copy these four cells
all the way down to row 22 (which should be opposite the 10 in column
A Where there are zeros in column E are the roots of the equation.
See if you can use the graph function of the spreadsheet to draw
the curve and then you can see where it crosses the line. The proper
way is to factor the equation into two brackets which multiply-out
to give the equation you have. Each of these two brackets could
equal zero in their own right to make the overall equation equal
zero (which is what you are looking for when you ask for the intersections).
For example X2-5X+6 can be factored to (X-2)*(X-3) so, either (x-2)
equals zero or (X-3) equals zero. So if X=2 then (X-2) will be zero
or if X=3 the (X-3) will equal zero. So the answers to this one
are 2 and 3. The key to factoring equations (where you just have
an X2 (and not 2X2 for example) is to find two numbers that multiply
together to give the constant (in your case -35) and add together
to give the X one (in your case -2). Because your constant is negative
you know that one of your factors will be a positive number and
the other one will be a negative one. Good luck! but if you still
cannot get it - ask again.
Brian
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