Find Coefficients in y=-x² + 3x + 40: Quadratic Equation Analysis

Quadratic Coefficients with Negative Leading Terms

Identify the coefficients based on the following equation

y=x2+3x+40 y=-x^2+3x+40

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:07 Let's find the coefficients of the function.
00:10 We're using the formula to show a quadratic equation.
00:19 First, separate the variable from its coefficient.
00:36 Next, compare the formula to our equation to find the coefficients.
00:50 And that's how we solve the question!

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

Identify the coefficients based on the following equation

y=x2+3x+40 y=-x^2+3x+40

2

Step-by-step solution

To solve this problem, we will follow these steps:

  • Step 1: Identify the given quadratic equation and its form.
  • Step 2: Directly match the coefficients of the given equation to the standard form y=ax2+bx+c y = ax^2 + bx + c .
  • Step 3: Compare with the provided choices and select the one that matches.

Now, let's work through each step:
Step 1: The given quadratic equation is y=x2+3x+40 y = -x^2 + 3x + 40 . This matches the form y=ax2+bx+c y = ax^2 + bx + c .

Step 2: By comparing the given equation to the standard form:
- The coefficient a a is the coefficient of x2 x^2 , which is 1-1.
- The coefficient b b is the coefficient of x x , which is 3 3 .
- The coefficient c c is the constant term, which is 40 40 .

Step 3: From the analysis, we identify a=1 a = -1 , b=3 b = 3 , c=40 c = 40 . We compare these with the provided choices.
The correct answer is: a=1,b=3,c=40 a=-1,b=3,c=40

Therefore, the solution to the problem matches choice 4.

3

Final Answer

a=1,b=3,c=40 a=-1,b=3,c=40

Key Points to Remember

Essential concepts to master this topic
  • Standard Form: Match y = ax² + bx + c exactly
  • Technique: For -x², the coefficient a = -1 (not 1)
  • Check: Verify -1(-4)² + 3(-4) + 40 = 12 ✓

Common Mistakes

Avoid these frequent errors
  • Ignoring the negative sign on x²
    Don't assume a = 1 when you see x² = wrong coefficient! The equation shows -x², which means the coefficient is -1. Always include the sign when identifying coefficients.

Practice Quiz

Test your knowledge with interactive questions

What is the value of the coefficient \( c \) in the equation below?

\( 4x^2+9x-2 \)

FAQ

Everything you need to know about this question

Why is the coefficient of x² equal to -1 and not 1?

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Because the equation shows -x², not +x². The coefficient includes the sign, so x2=1x2 -x^2 = -1 \cdot x^2 , making a = -1.

What if there's no number written in front of x²?

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When no number is shown, the coefficient is understood to be 1 or -1 depending on the sign. For -x², the coefficient is -1.

How do I remember which coefficient is which?

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Use the pattern y=ax2+bx+c y = ax^2 + bx + c : a goes with x², b goes with x, and c is the number by itself.

Can coefficients be negative?

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Absolutely! Coefficients can be positive, negative, or zero. Always include the sign when writing your answer.

What happens if I get the coefficients wrong?

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Wrong coefficients lead to incorrect graphs and solutions. The parabola opens the wrong way if you get the sign of a wrong!

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