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Rewrite the function by completing the square.

{:[f(x)=4x^(2)+12 x+9],[f(x)=◻(x+◻)^(2)+◻]:}

Rewrite the function by completing the square.\newlinef(x)=4x2+12x+9f(x)=(x+)2+ \begin{array}{l} f(x)=4 x^{2}+12 x+9 \\ f(x)=\square(x+\square)^{2}+\square \end{array}

Full solution

Q. Rewrite the function by completing the square.\newlinef(x)=4x2+12x+9f(x)=(x+)2+ \begin{array}{l} f(x)=4 x^{2}+12 x+9 \\ f(x)=\square(x+\square)^{2}+\square \end{array}
  1. Identify coefficients: Identify the quadratic and linear coefficients in the original function.\newlineThe original function is f(x)=4x2+12x+9f(x) = 4x^2 + 12x + 9. The quadratic coefficient (the coefficient of x2x^2) is 44, and the linear coefficient (the coefficient of xx) is 1212.
  2. Factor out quadratic coefficient: Factor out the quadratic coefficient from the x2x^2 and xx terms.\newlineTo complete the square, we need to factor out the quadratic coefficient from the x2x^2 and xx terms. This gives us:\newlinef(x)=4(x2+3x)+9f(x) = 4(x^2 + 3x) + 9.
  3. Find completion value: Find the value to complete the square.\newlineTo complete the square for the expression x2+3xx^2 + 3x, we need to add and subtract (b2a)2(\frac{b}{2a})^2, where aa is the coefficient of x2x^2 (which is 11 after factoring out the 44) and bb is the coefficient of xx (which is 33). So we calculate (321)2=(32)2=94(\frac{3}{2 \cdot 1})^2 = (\frac{3}{2})^2 = \frac{9}{4}.
  4. Add and subtract value: Add and subtract the value found inside the parentheses.\newlineWe add and subtract 94\frac{9}{4} inside the parentheses to complete the square:\newlinef(x)=4(x2+3x+9494)+9f(x) = 4\left(x^2 + 3x + \frac{9}{4} - \frac{9}{4}\right) + 9.
  5. Write perfect square trinomial: Write the perfect square trinomial and adjust the constant term.\newlineThe expression x2+3x+94x^2 + 3x + \frac{9}{4} is a perfect square trinomial, which can be written as (x+32)2(x + \frac{3}{2})^2. We also need to subtract the 94\frac{9}{4} that we added inside the parentheses, but since it's multiplied by 44, we subtract 4×944\times\frac{9}{4} from the constant term:\newlinef(x)=4(x+32)24×94+9f(x) = 4(x + \frac{3}{2})^2 - 4\times\frac{9}{4} + 9.
  6. Adjust constant term: Simplify the constant term.\newlineNow we simplify the constant term by subtracting 4(94)4\left(\frac{9}{4}\right) from 99:\newlinef(x)=4(x+32)29+9f(x) = 4\left(x + \frac{3}{2}\right)^2 - 9 + 9.\newlinef(x)=4(x+32)2+0f(x) = 4\left(x + \frac{3}{2}\right)^2 + 0.
  7. Simplify constant term: Write the final form of the function.\newlineThe function is now written in the form of a completed square:\newlinef(x) = 44(x + \frac{33}{22})^22.