Q. Complete the square to re-write the quadratic function in vertex form:y=x2−9x−3Answer: y=
Focus on x-terms: To complete the square, we first need to focus on the x-terms in the quadratic function. The function is y=x2−9x−3. We want to form a perfect square trinomial with the x-terms. To do this, we take the coefficient of the x-term, which is −9, divide it by 2, and then square the result.
Form perfect square trinomial: Dividing the coefficient of x, which is −9, by 2 gives us −4.5. Squaring −4.5 gives us 20.25. This is the number we will add and subtract inside the parentheses to complete the square.
Rewrite function with addition and subtraction: We rewrite the function by adding and subtracting 20.25 inside the parentheses: y=(x2−9x+20.25)−20.25−3. We have added 20.25 to complete the square and subtracted it immediately to keep the equation balanced.
Factor perfect square trinomial: Now we can factor the perfect square trinomial inside the parentheses: y=(x−4.5)2−20.25−3.
Combine constants: Next, we combine the constants outside the parentheses: −20.25−3=−23.25. So the function becomes y=(x−4.5)2−23.25.
Quadratic function in vertex form: We have now completed the square, and the quadratic function is in vertex form. The vertex form of the function is y=a(x−h)2+k, where (h,k) is the vertex of the parabola. In our case, a=1, h=4.5, and k=−23.25.
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