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Question 464457: please help me solve this problem.... thank you
A parabola has its axis parallel to the y-axis and contains the points (1,-1),(2,3) and (3,15). Find its equation. (HINT: An equation of such a parabola is in the form: y= ax^2 + bx + c ).
Answer by lwsshak3(11628)   (Show Source):
You can put this solution on YOUR website! A parabola has its axis parallel to the y-axis and contains the points (1,-1),(2,3) and (3,15). Find its equation.
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Ax^2+Bx+C=y
A(1^2)+B(1)+C=-1
A(2^2)+B(2)+C=3
A(3^2)+B(3)+C=15
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1) A+B+C=-1
2) 4A+2B+C=3
3) 9A+3B+C=15
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2) 4A+2B+C=3
1) A+B+C=-1
Subtract eq 1 fm eq 2 to eliminate C
4) 3A+B=4
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3) 9A+3B+C=15
2) 4A+2B+C=3
subtract eq 2 fm eq 3 to eliminate C
5) 5A+B=12
4) 3A+B=4
subtract eq 4 fm eq 5 to eliminate B
2A=8
A=4
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4) 3A+B=4
sub A
3(4)+B=4
B=4-12=-8
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1) A+B+C=-1
sub A and B
4-8+C=-1
C=3
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Check:
2) 4A+2B+C=3
4(4)+2(-8)+3=3
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3) 9A+3B+C=15
9(4)+3(-8)+3=15
..
A=4
B=-8
C=3
Equation:y=4x^2-8x+3
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