Write the equation of the parabola that passes through the points (–7,–7), (–5,0), and (–2,0).
Question
Write the equation of the parabola that passes through the points (–7,–7), (–5,0), and (–2,0).
Solution
To find the equation of the parabola that passes through the points (-7,-7), (-5,0), and (-2,0), we can use the general form of a parabola equation, which is y = ax^2 + bx + c.
We can substitute the given points into this equation to form a system of three equations to solve for a, b, and c.
Substituting (-7,-7) into the equation gives us: -7 = 49a - 7b + c ---- (1)
Substituting (-5,0) into the equation gives us: 0 = 25a - 5b + c ---- (2)
Substituting (-2,0) into the equation gives us: 0 = 4a - 2b + c ---- (3)
We can solve this system of equations using substitution or elimination method. Let's use elimination.
Subtract equation (2) from equation (1): -7 = 24a - 2b ---- (4)
Subtract equation (3) from equation (2): 0 = 21a - 3b ---- (5)
Multiply equation (4) by 3 and equation (5) by 2 to make the coefficients of b the same: -21 = 72a - 6b ---- (6) 0 = 42a - 6b ---- (7)
Subtract equation (7) from equation (6): -21 = 30a a = -21/30 = -7/10
Substitute a = -7/10 into equation (2): 0 = 25(-7/10) - 5b + c 0 = -175/10 - 5b + c 0 = -17.5 - 5b + c 17.5 = 5b - c ---- (8)
Substitute a = -7/10 into equation (3): 0 = 4(-7/10) - 2b + c 0 = -28/10 - 2b + c 0 = -2.8 - 2b + c 2.8 = 2b - c ---- (9)
Subtract equation (9) from equation (8): 14.7 = 3b b = 14.7/3 = 4.9
Substitute a = -7/10 and b = 4.9 into equation (1): -7 = 49(-7/10) - 7(4.9) + c -7 = -34.3 + c c = -7 + 34.3 = 27.3
So, the equation of the parabola is y = -7/10x^2 + 4.9x + 27.3.
Similar Questions
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