Math  /  Algebra

Question 2. y=x26x+5y=1212=x26x+51212x26x7=0\begin{array}{l} \text { 2. } y=x^{2}-6 x+5 \\ y=12 \\ \begin{array}{l} 12=x^{2}-6 x+5 \\ -12 \quad-12 \end{array} \\ x^{2}-6 x-7=0 \end{array}

Studdy Solution

STEP 1

1. The problem involves solving a quadratic equation.
2. The equation is given in the form y=x26x+5 y = x^2 - 6x + 5 and we need to find x x when y=12 y = 12 .
3. The quadratic equation can be solved by factoring, completing the square, or using the quadratic formula.

STEP 2

1. Substitute the given value of y y into the equation.
2. Rearrange the equation to standard quadratic form.
3. Solve the quadratic equation using an appropriate method.
4. Verify the solutions.

STEP 3

Substitute y=12 y = 12 into the equation y=x26x+5 y = x^2 - 6x + 5 :
12=x26x+5 12 = x^2 - 6x + 5

STEP 4

Rearrange the equation to standard quadratic form by moving all terms to one side:
12=x26x+5 12 = x^2 - 6x + 5 Subtract 12 from both sides:
x26x+512=0 x^2 - 6x + 5 - 12 = 0 x26x7=0 x^2 - 6x - 7 = 0

STEP 5

Solve the quadratic equation x26x7=0 x^2 - 6x - 7 = 0 . We will use the quadratic formula, which is given by:
x=b±b24ac2a x = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}
For the equation x26x7=0 x^2 - 6x - 7 = 0 , identify a=1 a = 1 , b=6 b = -6 , and c=7 c = -7 .

STEP 6

Calculate the discriminant b24ac b^2 - 4ac :
b24ac=(6)24(1)(7) b^2 - 4ac = (-6)^2 - 4(1)(-7) =36+28 = 36 + 28 =64 = 64

STEP 7

Substitute the values into the quadratic formula:
x=(6)±642(1) x = \frac{-(-6) \pm \sqrt{64}}{2(1)} x=6±82 x = \frac{6 \pm 8}{2}

STEP 8

Calculate the two possible values for x x :
x=6+82=142=7 x = \frac{6 + 8}{2} = \frac{14}{2} = 7 x=682=22=1 x = \frac{6 - 8}{2} = \frac{-2}{2} = -1

STEP 9

Verify the solutions by substituting back into the original equation y=x26x+5 y = x^2 - 6x + 5 to ensure they satisfy y=12 y = 12 .
For x=7 x = 7 :
y=726(7)+5=4942+5=12 y = 7^2 - 6(7) + 5 = 49 - 42 + 5 = 12
For x=1 x = -1 :
y=(1)26(1)+5=1+6+5=12 y = (-1)^2 - 6(-1) + 5 = 1 + 6 + 5 = 12
Both solutions are verified.
The solutions for x x are:
7 and 1 \boxed{7 \text{ and } -1}

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