Question 359435
standard equation:  y={{{ax^2+bx+c}}}
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you need 3 sets of points, any 3 of the 5 sets given will do.
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This will generate 3 equations in 3 unknowns
x=9, Y=5  plug this into the standard equation  5=81a+9b+c
x=10, y=10    plug into std equation   10=100a+10b+c
x=11, y=5     plug into std equation   5=121a+11b+c
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eq 1:   5=81a+9b+c
eq 2:  10=100a+10b+c
eq 3:  5=121a+11b+c
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eq 4: 5=19a+b   sub eq1 from eq2 to eliminate c
eq 5: 0=40a+2b  sub eq1 from eq3 to eliminate c
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-10=2a   multiply eq4 by -2 and add to eq 5 to eliminate b
a=-5
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substitute a=-5 into eq4 or eq5, i'll choose eq 5
0=40*(-5)+2b
0=-200+2b
200=2b
100=b
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substitute a=-5, b=100 into one of the 3 original equations, i'll choose eq1
5=81(-5)+9(100)+c
5=-405+900+c
5=495+c
c=-490
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a=-5, b=100, c=-490
substitute into the standard equation
y={{{-5x^2+100x-400}}}
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validate this equation by choosing a different point
x=12, y=-10

-5*(12)^2+100*12-490  does this equal y=-10????
i'll let you finish this validation