Question 206449
You first learn to multiply: 2*3=6
Then you learn to factor: 6=2*3 
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Your problem:
What I don't understand is why r^2-5r+6 factors to [(r-3)(r-2)]...
You first learn FOIL:
(r-3)(r-2)
F: r*r = r^2
O: r*-2= -2r
I: -3*r= -3r
L: -2*-3= 6
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Then you learn to factor:
r^2-5r+6
Think of two numbers whose product is 6 and whose sum is -5
The numbers are -2 and -3
Rewrite the problem replacing -5r by -3r-2r
r^2-3r-2r+6
Factor the 1st two and the last two terms separately:
r(r-3)-2(r-3)
Factor again to get the factored answer:
(r-3)(r-2)
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Hope that helps.
Cheers,
Stan H.