Write the quadratic function in the form \( y=a(x-h)^{2}+k \) and sketch its graph. \( y=x^{2}-4 x \)
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The Deep Dive
To rewrite the quadratic function \( y = x^2 - 4x \) in the form \( y = a(x-h)^2 + k \), we need to complete the square. 1. Start with \( y = x^2 - 4x \). 2. Take half of the coefficient of \( x \) (which is -4), square it, and add and subtract that value inside the function. Half of -4 is -2, and squaring it gives 4. 3. Rewrite the expression: \[ y = (x^2 - 4x + 4) - 4 = (x - 2)^2 - 4. \] So, in vertex form, this function is \( y = (x - 2)^2 - 4 \), where the vertex is \( (h, k) = (2, -4) \). Now sketching the graph: 1. The vertex is located at \( (2, -4) \). 2. The parabola opens upwards (since the coefficient of \( (x - 2)^2 \) is positive). 3. The axis of symmetry is the line \( x = 2 \). 4. For additional points, we can test \( x = 1 \) (which gives \( y = -3 \)), \( x = 3 \) (which also gives \( y = -3 \)), and \( x = 0 \) (which gives \( y = 4 \)). The graph looks like a 'U' shape opening upward with its vertex at \( (2, -4) \).