31 Things Girls Do That Give People the Ick (Plus, How to Stop Doing Them)
Q&A for How to Complete the Square
Coming soon
Search
-
QuestionWhy do you halve the b value and then square it? It makes no sense to me.Community AnswerIt does seem strange and arbitrary, but there is a reason for it. The power move is taking the square root of both sides, but you can't simplify the square root of most polynomials. The step you ask about is a setup move to make the power move work. If I have, for example, x^2 + 4x = 5, and take the square root of both sides, nothing happens, it just makes a mess. But if I add 4 to both sides first and take the square root of both sides of x^2 + 4x + 4 = 9, it simplifies to |x+2| = 3 and the quadratic equation is reduced to a linear equation.
-
QuestionWhat's the completing the square formula if x > 1?DonaganTop AnswererThe value of x doesn't matter. The process remains as shown above.
-
QuestionIn Part 1 of 2, how did you get 11/9 in Step 8?DonaganTop AnswererBoth sides of that equation are being divided by 3 (to get rid of the coefficient of the first term). Dividing the second term (11/3) by 3 gives us 11/9.
-
QuestionWhat if there is no coefficient?DonaganTop AnswererWhen no coefficient is shown, you can consider the coefficient to be 1.
-
QuestionWhat should be added to 11111 to make it a perfect square, and how?DonaganTop AnswererUse a calculator to find the square root of 11,111. It's about 105.4. Take the next higher whole number (106), square it (11,236), then subtract 11,111 to find your answer.
-
QuestionI'm trying to "rewrite the function by completing the square", but I don't know how to do it when the coefficient isn't one, like with 4x^2 - 28x + 49. Any help?DonaganTop AnswererNotice that 4 and 49 are both perfect squares. So the factors you'll use for 4 will be either 2 and 2 or -2 and -2. The factors for 49 will be either 7 and 7 or -7 and -7. You'll have to multiply the 2's and the 7's together and add them to arrive at -28. Notice that 2 x -7 equals -14, and two of those would add to make -28. So the factors would be (2x - 7) and (2x - 7) or (2x - 7)². Note that you could change the signs in your factors and still get the same result: (7 - 2x)(7 - 2x) also equals 4x² - 28x + 49. So you could write the final answer as +/-(2x-7)².
-
QuestionHow do we find the least value of 2x^2-x+6 and the value of x at which this occurs?Community AnswerSolve it graphically. Plot the graph of that function, and note the coordinates of the vertex (which is a minimum). The y coordinate of the vertex is the lowest value of the function, and the x coordinate of the vertex is the x value at which this lowest y-value occurs.
Ask a Question
200 characters left
Include your email address to get a message when this question is answered.
Submit