Q. If the factors of the quadratic function (g) are (x – 7) and (x + 3), what are the zeros of function (g)?

Answer

Given \( (x-7)(x+3)=0 \).
Solve \(x-7=0\Rightarrow x=7\) and \(x+3=0\Rightarrow x=-3\).
Zeros: \(7,\ -3\).

Detailed Explanation

Step 1 — Definition of a zero. A zero of the function g is any real number x for which g(x) = 0.

Step 2 — Express g(x) using its factors. If the given factors of g are (x − 7) and (x + 3), then g(x) has the form \(g(x)=k(x-7)(x+3)\) for some constant \(k\neq 0\). The constant factor \(k\) does not affect the zeros.

Step 3 — Set the function equal to zero and apply the zero-product property. To find zeros we solve \(g(x)=0\), which gives

\((x-7)(x+3)=0\)

The zero-product property states that if a product of two factors equals zero, then at least one of the factors must be zero. Thus we solve the two simple equations separately:

  1. Solve \(x-7=0\), which yields \(x=7\).
  2. Solve \(x+3=0\), which yields \(x=-3\).

Step 4 — Verify by substitution (optional check).

  • For \(x=7\): \((7-7)(7+3)=0\cdot 10=0\).
  • For \(x=-3\): \((-3-7)(-3+3)=(-10)\cdot 0=0\).

Conclusion. The zeros of g are \(x=7\) and \(x=-3\).

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Algebra FAQs

What are the zeros of \(g\) if the factors are \(x-7\) and \(x+3\)?

The zeros are found by setting each factor to zero: \(x-7=0\) which implies \(x=7\) and \(x+3=0\) which implies \(x=-3\)..

How do you write \(g(x)\) from the factors?

Multiply the factors: \(g(x)=(x-7)(x+3)=x^2-4x-21\).

What is the axis of symmetry and the vertex of this quadratic?

Axis of symmetry is \(x=\frac{7+(-3)}{2}=2\). Vertex: \(g(2)=2^2-4\cdot2-21=-25\), so vertex \((2,-25)\).

What is the y-intercept of \(g(x)\)?.

Set \(x=0\): \(g(0)=(0-7)(0+3)=-21\). Y-intercept is \((0,-21)\).

What are the sum and product of the zeros, and how do they relate to coefficients?

Sum: \(7+(-3)=4\), equals \(-\frac{b}{a}\). Product: \(7\cdot(-3)=-21\), equals \(\frac{c}{a}\) for \(ax^2+bx+c\)..

What happens if a factor is repeated (multiplicity)?

What happens if a factor is repeated (multiplicity)?

How can you check the zeros by expanding and solving?

Expand to get \(x^2-4x-21=0\). Solve by factoring or quadratic formula; factoring yields \((x-7)(x+3)=0\) so \(x=7,-3\).

What is the end behavior of this quadratic function?

Leading coefficient is positive (1), so as \(x\to\pm\infty\), \(g(x)\to+\infty\); the parabola opens upward.
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