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Math Help - quadractics, help

  1. #1
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    quadractics, help

    Quadratics Assignment HELP!
    Hello, im doing this quadratics math assingment, i have not been able to resolve the next three questions. Could someone please help me out? i would be extremely grateful

    1. Consider the function, f(x)= -4x^2 -16x -7
    a)Determine the y-intercept
    b)Determine the vertex
    c) Determine the x-intercepts

    (When i tried this one i converted the stantard form to vertex form, but im not sure if i did it right, and then to get the x intercepts i tried the Australian method to convert it to factored form but i failed, so im all confused now)

    2. Simplify the following expression:

    √18 + √20 + √12 + √32
    ----- ---- ---- -----
    √50 √45 √75 √18

    (the thing infront of the numbers is the square root sign)




    3. Determine the value(s) of K, such that the quadratic equation
    0= x^2 + kx + k + 15


    pleasee, help i need to understand how to resolve this
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  2. #2
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    Quote Originally Posted by MonaMath View Post
    ...

    2. Simplify the following expression:

    √18 + √20 + √12 + √32
    ----- ---- ---- -----
    √50 √45 √75 √18

    (the thing infront of the numbers is the square root sign)

    ...
    You can calculate the square root partially(?):

    \dfrac{\sqrt{18}}{\sqrt{50}}+\dfrac{\sqrt{20}}{\sq  rt{45}}+\dfrac{\sqrt{12}}{\sqrt{75}}+\dfrac{\sqrt{  32}}{\sqrt{18}} =  <br />
\dfrac{\sqrt{9\cdot 2}}{\sqrt{25\cdot 2}}+\dfrac{\sqrt{4\cdot 5}}{\sqrt{9\cdot 5}}+\dfrac{\sqrt{4\cdot 3}}{\sqrt{25\cdot 3}}+\dfrac{\sqrt{16\cdot 2}}{\sqrt{9\cdot 2}}

    Now calculate the square root of the squares and cancel the common factors.
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  3. #3
    A riddle wrapped in an enigma
    masters's Avatar
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    Quote Originally Posted by MonaMath View Post
    Quadratics Assignment HELP!
    Hello, im doing this quadratics math assingment, i have not been able to resolve the next three questions. Could someone please help me out? i would be extremely grateful

    1. Consider the function, f(x)= -4x^2 -16x -7
    a)Determine the y-intercept
    b)Determine the vertex
    c) Determine the x-intercepts

    (When i tried this one i converted the stantard form to vertex form, but im not sure if i did it right, and then to get the x intercepts i tried the Australian method to convert it to factored form but i failed, so im all confused now)

    2
    Hello Mona,

    (1) f(x)=-4x^2-16x-7

    f(x)=-4(x^2+4x+4)-7+16

    f(x)=(x+2)^2+9

    V(-2, 9)

    To find the y-intercept, find f(0).

    f(0)=-4(0)^2-16(0)-7=-7

    To find the zeros, set f(x)=0 and solve for x.

    -4x^2-16x-7=0

    4x^2+16x+7=0

    (2x+7)(2x+1)=0

    x=-\frac{7}{2} \ \ or \ \ x=-\frac{1}{2}
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