Math

Congrats to caledonia unplugged who got last weeks Math problem correct!!

0.59375 as a fraction is 19/32.

This week’s is all about algebra.

Solve for x…and show your work! ;^)

x^2 + x – 2 = 0

(hint: the carrot (^) between the x and the 2 means “raised to” or in other words “x^2” means “x squared.”)

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6 comments so far

  1. Brenda on

    x^2 +x -2 = 0

    Factor trinomial which geives us the following:

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

    Since any number times 0 is 0, solve each sub equation for 0.

    Solve first part for 0:

    -x – 2 = 0
    -x = 2

    Solve second part for 0:
    -x +1 =0
    -x =-1
    x=1

    So the solution set is x = {-2,1}

  2. gopfolk on

    WAY TO GO BRENDA!!!!!

    And thanks for showing your work! :^)

  3. steveegg on

    Math via the quadratic equation (useful when one cannot factor that equation neatly) –

    x = (-b +/- (b^2 – 4ac)^.5) / 2a (kind of hard to do this with Blogger’s limited HTML tag set)

    Since the equation is already in the form ax^2 + bx + c = 0, a = 1, b = 1 and c = -2.

    Positive x = (-1 + (1^2 – 4(1)(-2))^.5) / 2(1)
    = (-1 + (1 – (-8))^.5) / 2
    = (-1 + (9)^.5) / 2
    = (-1 + 3) / 2
    = 2 / 2
    = 1

    Negative x = (-1 – (1^2 – 4(1)(-2))^.5) / 2(1)
    = (-1 – (1 – (-8))^.5) / 2
    = (-1 – (9)^.5) / 2
    = (-1 – 3) / 2
    = -4 / 2
    = -2

    Since we’re talking math, the solution set is the same as factoring: x = {-2, 1}

  4. steveegg on

    I should have explained for the record that “(number)^.5” is the positive square root of said number (can’t create the root symbol)

  5. gopfolk on

    I should have explained for the record that “(number)^.5” is the positive square root of said number (can’t create the root symbol)

    There was no need to explain…I’m thinking that we all understood.

    But for the record, I’m going to have to move to harder problems since you guys seem to think this is so easy. 😉

  6. Brenda on

    I always hated quadratic equations in school but thanks Steve for showing how to use it for this example!!!

    As you pointed out, sometimes the equation cannot be factored neatly!!


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