Put the quadratic
[tex]\[ y = 3x^2 + 5x + 1 \][/tex]
into the quadratic formula: [tex]\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \][/tex]

Choose the number that belongs in the green box.
[tex]\[ x = \frac{-5 \pm \sqrt{[?]^2 - 4[]}}{2} \][/tex]

A. 5
B. 1
C. 3
D. 2



Answer :

Let's solve the problem step-by-step.

1. Identify the coefficients from the quadratic equation:

The given quadratic equation is:
[tex]\[ y = 3x^2 + 5x + 1 \][/tex]

From this equation, we can identify the coefficients:
[tex]\[ a = 3, \quad b = 5, \quad c = 1 \][/tex]

2. Recall the quadratic formula:

The quadratic formula to find the roots of a quadratic equation of the form [tex]\( ax^2 + bx + c = 0 \)[/tex] is given by:
[tex]\[ x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} \][/tex]

3. Substitute the coefficients into the quadratic formula:

In our case, substituting [tex]\( a = 3 \)[/tex], [tex]\( b = 5 \)[/tex], and [tex]\( c = 1 \)[/tex]:
[tex]\[ x = \frac{-5 \pm \sqrt{5^2 - 4 \cdot 3 \cdot 1}}{2 \cdot 3} \][/tex]

4. Determine the number in the green box:

The expression under the square root [tex]\(b^2 - 4ac\)[/tex] simplifies to [tex]\(5^2 - 4 \cdot 3 \cdot 1\)[/tex], which we've identified as the value 13. However, the question asks for the value to put into the green box, which references the first part of the discriminant [tex]\(b\)[/tex].

Therefore, the correct substitution for determining the number to place in the green box is:
[tex]\[ x = \frac{-5 \pm \sqrt{5^2 - 4(3)(1)}}{2(3)} \][/tex]

So, the number that belongs in the green box is:
[tex]\[ 5 \][/tex]

Thus, the correct answer is:
[tex]\[ 5 \][/tex]

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