Solve the equation:

[tex]\[
\begin{array}{l}
(8+x)(10-x)=77 \\
80 - 8x + 10x - x^2 = 77 \\
80 + 2x - x^2 = 77 \\
0 = x^2 - 2x + 77 - 80 \\
0 = x^2 - 2x - 3
\end{array}
\][/tex]



Answer :

To solve the quadratic equation \( (-x^2 + 2x + 77 - 80) = 0 \) that simplifies to \( x^2 - 2x - 3 = 0 \), let's follow these steps closely:

1. Identify the quadratic equation:
The given equation is \( x^2 - 2x - 3 = 0 \).

2. Solve the quadratic equation:
To solve this quadratic equation, we look for values of \( x \) that satisfy the equation. One common method is to factorize the quadratic expression.

3. Factorize the quadratic expression:
We need two numbers that multiply to \(-3\) (the constant term) and add up to \(-2\) (the coefficient of the linear term). These two numbers are \(-3\) and \(1\). Therefore, we can rewrite the quadratic expression as:
[tex]\[ x^2 - 3x + x - 3 = 0 \][/tex]
Next, we group the terms to factor by grouping:
[tex]\[ (x^2 - 3x) + (x - 3) = 0 \][/tex]
Factor out the common terms:
[tex]\[ x(x - 3) + 1(x - 3) = 0 \][/tex]

4. Apply the zero product property:
We see that the factored form is:
[tex]\[ (x - 3)(x + 1) = 0 \][/tex]
Using the zero-product property, we set each factor equal to zero:
[tex]\[ x - 3 = 0 \quad \text{or} \quad x + 1 = 0 \][/tex]
Solving these equations gives:
[tex]\[ x = 3 \quad \text{or} \quad x = -1 \][/tex]

So, the solutions to the quadratic equation [tex]\( x^2 - 2x - 3 = 0 \)[/tex] are [tex]\( x = 3 \)[/tex] and [tex]\( x = -1 \)[/tex].

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