Find the Coefficient b in 3x²+8x-5: Quadratic Expression Analysis

Quadratic Coefficients with Standard Form Identification

What is the value of the coefficient b b in the equation below?

3x2+8x5 3x^2+8x-5

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Step-by-step video solution

Watch the teacher solve the problem with clear explanations
00:00 Find the value of coefficient B in the equation
00:03 We'll use the formula to represent a quadratic equation
00:08 We can see that coefficient B is of X
00:15 We'll compare the formula to our equation and find the coefficients
00:24 And this is the solution to the question

Step-by-step written solution

Follow each step carefully to understand the complete solution
1

Understand the problem

What is the value of the coefficient b b in the equation below?

3x2+8x5 3x^2+8x-5

2

Step-by-step solution

The quadratic equation of the given problem is already arranged (that is, all the terms are found on one side and the 0 on the other side), thus we approach the given problem as follows;

In the problem, the question was asked: what is the value of the coefficientb b in the equation?

Let's remember the definitions of coefficients when solving a quadratic equation as well as the formula for the roots:

The rule says that the roots of an equation of the form

ax2+bx+c=0 ax^2+bx+c=0 are :

x1,2=b±b24ac2a x_{1,2}=\frac{-b\pm\sqrt{b^2-4ac}}{2a}

That is the coefficientb b is the coefficient of the term in the first power -x x We then examine the equation of the given problem:

3x2+8x5=0 3x^2+8x-5 =0 That is, the number that multiplies

x x is

8 8 Consequently we are able to identify b, which is the coefficient of the term in the first power, as the number8 8 ,

Thus the correct answer is option d.

3

Final Answer

8

Key Points to Remember

Essential concepts to master this topic
  • Standard Form: In ax2+bx+c=0 ax^2 + bx + c = 0 , identify coefficient positions
  • Technique: For 3x2+8x5 3x^2 + 8x - 5 , coefficient b multiplies the x term
  • Check: Verify b = 8 by matching 8x 8x to the bx position ✓

Common Mistakes

Avoid these frequent errors
  • Confusing coefficient positions in quadratic expressions
    Don't think the first number (3) is always coefficient b = wrong identification! Students often assume coefficients go in alphabetical order. Always remember: in ax2+bx+c ax^2 + bx + c , coefficient b specifically multiplies the x term.

Practice Quiz

Test your knowledge with interactive questions

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

\( 3x^2+8x-5 \)

FAQ

Everything you need to know about this question

What does each coefficient represent in a quadratic?

+

In the standard form ax2+bx+c=0 ax^2 + bx + c = 0 :

  • a is the coefficient of x2 x^2
  • b is the coefficient of x x
  • c is the constant term

Why is b = 8 and not b = 3 in this problem?

+

Look at what each number multiplies! In 3x2+8x5 3x^2 + 8x - 5 :

  • 3 multiplies x2 x^2 (so a = 3)
  • 8 multiplies x (so b = 8)
  • -5 is alone (so c = -5)

What if the x term was negative, like -8x?

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Then b = -8! The coefficient includes the sign in front of the term. Always look at the complete coefficient, including any negative signs.

Does the order of terms matter for identifying coefficients?

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No! Whether it's 3x2+8x5 3x^2 + 8x - 5 or 8x+3x25 8x + 3x^2 - 5 , coefficient b is still 8 because it's what multiplies the x term.

What if there's no x term in the quadratic?

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Then b = 0! For example, in 2x27 2x^2 - 7 , there's no x term, so we can write it as 2x2+0x7 2x^2 + 0x - 7 , making b = 0.

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