? asked in Science & MathematicsMathematics · 1 decade ago

This is just embarrassing..?

Solve by Factoring: 4x2 - 16 = 0

Solve by Factoring: 2x2 + 5x - 3 = 0

Solve by Factoring: x2 + 5x - 6 = 0

Solve by Factoring: 3x2 = -9x

I just picked up my kids text book and i can not do this it is frustrating that 15 year old is smarter than me!

Update:

Thank You now my kid wont have bragging rights hahaha

12 Answers

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  • Anonymous
    1 decade ago
    Favorite Answer

    Go here to learn how to factor quadratics:

    http://www.purplemath.com/modules/factquad.htm

  • ?
    Lv 7
    1 decade ago

    Solve by Factoring: 4x2 - 16 = 0, (2*x + 4)*(2*x - 4) = 0

    Solve by Factoring: 2x2 + 5x - 3 = 0, (2*x - 1)*(x + 3)

    Solve by Factoring: x2 + 5x - 6 = 0, (x + 6)*(x - 1)

    Solve by Factoring: 3x2 = -9x , 3*x^2 + 9*x = 0, 3*x(x + 3) = 0

  • 1 decade ago

    1. 4x^2 - 16 = (2x)^2 - 4^2 = (2x+4) (2x-4)

    2x+4 = 0, 2x-4 = 0

    x = 2, -2

    2. 2x^2 + 5x- 3 = (x+3) (2x-1)

    x+3 =0, 2x-1=0

    x = -3, 1/2

    3. x^2 + 5x - 6 = (x+6) (x-1)

    x + 6 = 0, x - 1 = 0

    x = -6, 1

    4. 3x^2 = -9x

    3x^2 + 9x = 0

    3x (x+3) = 0

    3x = 0, x+3 =0

    x = 0, -3

    Note: In all cases, factorization can be done easily by finding two numbers whose sum is the coefficient of x term and product is the constant term (the one that does not contain x)

  • 1 decade ago

    4x2 - 16 = 0

    ==> (2x -4) (2x + 4) = 0

    ==> 2(x-2) (x+2) = 0

    ==> x = 2 or x = -2

    x2 + 5x - 6 = 0

    ==> x^2 + 6x - x -6 = 0

    ==> x(x +6) -1(x+6) = 0

    ==> (x+6) (x -1) = 0

    ==> x = -6 or x = 1

    3x2 = -9x

    ==> 3x^2 - 9x = 0

    ==> 3x(x -3) = 0

    ==> x = 3

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  • 1 decade ago

    4x2 - 16 = 0

    USE FORMULA a^2 - b^2 = ( a + b) ( a- b)

    Here a = 2x

    b = 4

    ( 2x + 4) ( 2x- 4 ) = 0

    So EITHER

    2x - 4 = 0

    i.e. 2x = 4

    x = 2

    OR

    ( 2x + 4) = 0

    2x = -4

    x = -2

    ANSWER x = +2 , -2

    2) 2x^2 + 5x - 3 = 0

    COEFF of x^2 = +2

    ( +2) ( -3) = -6

    FIND FACTORS OF -6 which add up to + 5 ( COEFF of x )

    (+6) ( -1)

    2x^2 + 6x - x -3 = 0

    2x ( x + 3) - 1( x + 3) = 0

    ( 2x -1) ( x+ 3) = 0

    ANSWER x = -3, 1/2

    3) x^2 + 5x - 6 = 0

    x^2 + 6x - x - 6 = 0

    x ( x + 6 ) -1 ( x + 6 ) = 0

    ( x - 1) ( x+ 6) = 0

    ANSWER x = 1 , -6

    4) 3x^2 = -9x

    3x^2 + 9x = 0

    3x ( x + 3) = 0

    ANSWER x = 0 , -3

  • Anonymous
    1 decade ago

    4x2 - 16 = 0

    4(x2 - 4) = 0

    4(x - 2)(x + 2) = 0

    x = 2, -2 --> This is because 4(2 - 2)(2 + 2) = 0 and 4(-2 - 2)(-2 + 2) = 0

    2x2 + 5x - 3 = 0

    (2x - 1)(x + 3) = 0

    x = 1/2, -3

    x2 + 5x - 6 = 0

    (x - 1)(x - 5) = 0

    x = 1, 5

    3x2 = -9x

    3x2 + 9x = 0

    3x(x + 3) = 0

    x = -3, 0

  • 1 decade ago

    1. 4(x^2 - 4) = 0 = 4(x+2)(x-2), x = -2 or 2

    2. (2x - 1)(x + 3) = 0, x = 1/2 or -3

    3. (x + 6)(x - 1) = 0, x = -6 or 1

    4. 3x^2 - 9x = 0 = 3x(x - 3), x = 0 or -3

  • iceman
    Lv 7
    1 decade ago

    4x^2 - 16 = 0

    4(x^2 - 4) = 0

    4(x + 2)(x - 2) = 0

    x = -2, 2

    x^2 + 5x - 6 = 0

    (x + 6)(x - 1) = 0

    x = -6, 1

  • norman
    Lv 7
    1 decade ago

    4(x^2-4) = 4(x+2)(x-2)=0 x = -2,2

    (2x-1)(x+3)=0, x = 1/2, -3

    (x+6)(x-1)=0, x=-6,1

    3x^2 +9x = 0

    3x(x+3) = 0, x=0, -3

  • 1 decade ago

    4(x^2-4)=0

    4(x-2)(x+2)=0 x=2 x=-2

    2x^2+5x-3=0

    (2x-1)(x+3)=0 x=1/2 x=-3

    x^2+5x-6=0 (x+6)(x-1)=0 x=-6 x=1

    3x^2=-9x

    x^2=-3x

    x= +/- sq rt 3x

  • 1 decade ago

    1 is 4 (x-2) (x+2) = 0

    Solutions:

    x = -2

    x = 2

    Use wolfram-alpha to solve all math problems

    http://www30.wolframalpha.com/input/?i=4+x^2+-+16+...

    2 is (x+3) (2 x-1) = 0

    Solutions:

    x = -3

    x = 1/2

    http://www30.wolframalpha.com/input/?i=2x2+%2B+5x+...

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