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Thread: Help x-intercepts

  1. #1

    Help x-intercepts

    1. What are the x-intercepts of y=(x−2)(x+5) ?



    • A. (0, 2) and (0, -5)
    • B. (0, -2) and (0, 5)
    • C. (-2, 0) and (5, 0)
    • D. (2, 0) and (-5, 0)



    answer is D
    X-2=>
    X=2 (2,0)

    X+5=0
    X=-5 (-5,0)

    Correct or not





    1. Which of these quadratic functions has exactly one x -intercept?



    • A. y=x 2 −9
    • B. y=x 2 −6x+9
    • C. y=x 2 −5x+6
    • D. y=x 2 +x−6


    MY ANSWER IS

    A

    (X-#)(X+3)

    CORRECT OR NOT





    1. Which of the following parabolas opens upward and appears narrower than y=−3x 2 +2x−1 ?



    • A. y= 4x 2 −2x−1
    • B. y= −4x 2 +2x−1
    • C. y= x 2 +4x


    D. y= −2x 2 +x+

    MY ANSWER IS

    A

    CORRECT OR NOT

    THANKS MUCH

  2. #2
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    Quote Originally Posted by yorkmanz View Post
    1. What are the x-intercepts of y=(x−2)(x+5) ?



    • A. (0, 2) and (0, -5)
    • B. (0, -2) and (0, 5)
    • C. (-2, 0) and (5, 0)
    • D. (2, 0) and (-5, 0)



    answer is D
    X-2=>
    X=2 (2,0)

    X+5=0
    X=-5 (-5,0)

    Correct or not





    1. Which of these quadratic functions has exactly one x -intercept?



    • A. y=x 2 −9
    • B. y=x 2 −6x+9
    • C. y=x 2 −5x+6
    • D. y=x 2 +x−6


    MY ANSWER IS

    A

    (X-#)(X+3)

    CORRECT OR NOT ...... Don't know - because the equations you posted above are not quadratic equations





    1. Which of the following parabolas opens upward and appears narrower than y=−3x 2 +2x−1 ?



    • A. y= 4x 2 −2x−1
    • B. y= −4x 2 +2x−1
    • C. y= x 2 +4x


    D. y= −2x 2 +x+

    MY ANSWER IS

    A

    CORRECT OR NOT..... Don't know - because the equations you posted above are not quadratic equations

    THANKS MUCH
    You are not posting correct problems.

    As posted. you do not have a quadratic equation.

    In your other post, I guessed the correct equation and posted it.

    Now it is your turn - you will need to post correct problems.
    Last edited by Subhotosh Khan; 01-11-2019 at 08:17 PM.
    “... mathematics is only the art of saying the same thing in different words” - B. Russell

  3. #3
    Quote Originally Posted by Subhotosh Khan View Post
    You are not posting correct problems.

    As posted. you do not have a quadratic equation.

    In your other post, I guessed the correct equation and posted it.

    Now it is your turn - you will need to post correct problems.




    1. Which of these quadratic functions has exactly one x -intercept?





    • A. y=x^2 −9
    • B. y=x^2−6x+9
    • C. y=x^2 −5x+6
    • D. y=x^2 +x−6



    MY ANSWER IS

    A



    CORRECT OR NOT ...... Don't know - because the equations you posted above are not quadratic equations




    2. Which of the following parabolas opens upward and appears narrower than y=−3x 2 +2x−1 ?




    • A. y= 4x^2 −2x−1
    • B. y= −4x^2 +2x−1
    • C. y= x^2 +4x

    D. y= −2x^2 +x+

    MY ANSWER IS

    A

    CORRECT OR NOT..... Don't know - because the equations you posted above are not quadratic equations



    x^2 is quadric


    THANKS



  4. #4
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    Quote Originally Posted by yorkmanz View Post
    1. Which of these quadratic functions has exactly one x -intercept?





    • A. y=x^2 −9
    • B. y=x^2−6x+9
    • C. y=x^2 −5x+6
    • D. y=x^2 +x−6



    MY ANSWER IS

    A ............................ A has two x-intercepts x=3 and x=-3



    CORRECT OR NOT ....Incorrect




    2. Which of the following parabolas opens upward and appears narrower than y=−3x?2 +2x−1 ?.......?




    • A. y= 4x^2 −2x−1
    • B. y= −4x^2 +2x−1
    • C. y= x^2 +4x

    D. y= −2x^2 +x+ ? ............................................

    MY ANSWER IS

    A

    CORRECT OR NOT..... Don't know





    .
    “... mathematics is only the art of saying the same thing in different words” - B. Russell

  5. #5
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    Quote Originally Posted by yorkmanz View Post
    1. What are the x-intercepts of y=(x−2)(x+5) ?



    • A. (0, 2) and (0, -5)
    • B. (0, -2) and (0, 5)
    • C. (-2, 0) and (5, 0)
    • D. (2, 0) and (-5, 0)



    answer is D
    X-2=>
    X=2 (2,0)

    X+5=0
    X=-5 (-5,0)

    Correct or not
    Yes, that is correct. An "x- intercept" is a point on the graph where the graph crosses ("intersects") the x-axis. There y= 0. If y= (x- 2)(x+ 5)= 0 then either x- 2= 0 or x+ 5= 0. If x- 2= 0 then x= 2. If x+ 5= 0 then x= -5. In either case y= 0 so the x-intercepts are (2, 0) and (-5, 0).




    1. Which of these quadratic functions has exactly one x -intercept?



    • A. y=x 2 −9
    • B. y=x 2 −6x+9
    • C. y=x 2 −5x+6
    • D. y=x 2 +x−6


    MY ANSWER IS

    A

    (X-#)(X+3)

    CORRECT OR NOT
    No, that is not correct
    A. [tex]y= x^2- 9= (x- 3)(x+ 3)= 0[/tex]. We have either x- 3= 0 so x= -3 or x+ 3= 0 so x= -3. The two x-intercepts are (3, 0) and (-3, 0).
    B. [tex]y= x^2- 6x+ 9= (x- 3)^2= 0[/tex]. We must have x= 3. There is only one x-intercept.
    C. [tex]y= x^2- 5x+ 6= (x- 3)(x- 2)= 0[/tex]. We must have either x- 3= 0 so x= 3 or x- 2= 0 so x= 2. The two x-intercepts are (3, 0) and (2, 0).
    D. [tex]y= x^2+ x- 6= (x+ 3)(x- 2)= 0[/tex]. We must have either x+ 3= 0 so x= -3 or x- 2= 0 so x= 2. The two x-intercepts are (-3, 0) and (2, 0).
    The correct answer is B.



    1. Which of the following parabolas opens upward and appears narrower than y=−3x 2 +2x−1 ?



    • A. y= 4x 2 −2x−1
    • B. y= −4x 2 +2x−1
    • C. y= x 2 +4x


    D. y= −2x 2 +x+

    MY ANSWER IS

    A

    CORRECT OR NOT
    Yes, that is correct.
    A parabola opens upward if and only if its leading coefficient (the coefficient of [tex]x^2[/tex]) is positive. That is true in A and C. How "narrow" a parabola appears depends upon how large the absolute value of the leading coefficient is. The larger the leading coefficient, the "narrower" the parabola is. |4|= 4 is larger than |-3|= 3 while |1|= 1 is not.

    THANKS MUCH

  6. #6
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    Quote Originally Posted by HallsofIvy View Post
    … An "x- intercept" is a point on the graph where the graph crosses ("intersects") the x-axis …
    Rather than using "crosses the axis" or "intersects the axis", I prefer a phrase like "crosses or just touches the axis".

    The word "crosses" (in particular) can imply for beginning students that curves always continue on the other side of the axis, which we know is not always the case.

  7. #7
    Quote Originally Posted by HallsofIvy View Post
    Yes, that is correct. An "x- intercept" is a point on the graph where the graph crosses ("intersects") the x-axis. There y= 0. If y= (x- 2)(x+ 5)= 0 then either x- 2= 0 or x+ 5= 0. If x- 2= 0 then x= 2. If x+ 5= 0 then x= -5. In either case y= 0 so the x-intercepts are (2, 0) and (-5, 0).


    No, that is not correct
    A. [tex]y= x^2- 9= (x- 3)(x+ 3)= 0[/tex]. We have either x- 3= 0 so x= -3 or x+ 3= 0 so x= -3. The two x-intercepts are (3, 0) and (-3, 0).
    B. [tex]y= x^2- 6x+ 9= (x- 3)^2= 0[/tex]. We must have x= 3. There is only one x-intercept.
    C. [tex]y= x^2- 5x+ 6= (x- 3)(x- 2)= 0[/tex]. We must have either x- 3= 0 so x= 3 or x- 2= 0 so x= 2. The two x-intercepts are (3, 0) and (2, 0).
    D. [tex]y= x^2+ x- 6= (x+ 3)(x- 2)= 0[/tex]. We must have either x+ 3= 0 so x= -3 or x- 2= 0 so x= 2. The two x-intercepts are (-3, 0) and (2, 0).
    The correct answer is B.




    Yes, that is correct.
    A parabola opens upward if and only if its leading coefficient (the coefficient of [tex]x^2[/tex]) is positive. That is true in A and C. How "narrow" a parabola appears depends upon how large the absolute value of the leading coefficient is. The larger the leading coefficient, the "narrower" the parabola is. |4|= 4 is larger than |-3|= 3 while |1|= 1 is not.

    Thank you man .. that's a perfect explanation...

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