Math Problem Statement

The curve y=ax square +bx passes through (2,0) and (4,8) Find a and b

Solution

We are given the curve equation y=ax2+bxy = ax^2 + bx and two points: (2,0)(2, 0) and (4,8)(4, 8). Using these points, we can set up a system of equations to solve for aa and bb.

Step 1: Use the point (2,0)(2, 0)

Substitute x=2x = 2 and y=0y = 0 into the equation y=ax2+bxy = ax^2 + bx:

0=a(22)+b(2)0 = a(2^2) + b(2) 0=4a+2b0 = 4a + 2b 2a+b=0(Equation 1)2a + b = 0 \quad \text{(Equation 1)}

Step 2: Use the point (4,8)(4, 8)

Substitute x=4x = 4 and y=8y = 8 into the equation y=ax2+bxy = ax^2 + bx:

8=a(42)+b(4)8 = a(4^2) + b(4) 8=16a+4b8 = 16a + 4b 4a+b=2(Equation 2)4a + b = 2 \quad \text{(Equation 2)}

Step 3: Solve the system of equations

From Equation 1: 2a+b=02a + b = 0, we can express bb in terms of aa: b=2ab = -2a

Substitute this into Equation 2: 4a+(2a)=24a + (-2a) = 2 2a=22a = 2 a=1a = 1

Now, substitute a=1a = 1 into b=2ab = -2a: b=2(1)=2b = -2(1) = -2

Final Answer:

The values of aa and bb are: a=1,b=2a = 1, \quad b = -2

Would you like a further explanation of any of the steps or additional details?


Here are 5 questions that expand on this concept:

  1. How would the curve change if b=0b = 0?
  2. Can we find the vertex of the parabola y=ax2+bxy = ax^2 + bx?
  3. How do the signs of aa and bb affect the shape of the parabola?
  4. What happens if the points (2,0)(2, 0) and (4,8)(4, 8) are switched?
  5. How do you determine whether the curve opens upwards or downwards?

Tip: When solving systems of equations, always try to express one variable in terms of the other to simplify the substitution process.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Systems of Equations

Formulas

Quadratic equation: y = ax^2 + bx
Substitution method for systems of equations

Theorems

None directly, but involves solving a system of linear equations derived from a quadratic expression

Suitable Grade Level

Grades 9-11