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Trying to help daughter solve this easy one.....?

Need to solve:

(3x-4)(2x+7)

please show steps.

Thanks

10 Answers

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  • 1 decade ago
    Favorite Answer

    You need to multiply each term to the other

    (3x)(2x) + (3x)(7) - (4) (2x) - (4)(7)

    6x^2 + 21x - 8x - 28

    6x^2 + 13x - 28

    Good luck

  • jim n
    Lv 4
    1 decade ago

    There is something missing from the problem as stated.

    Did you mean

    (1) Solve (3x-4)(2x+7) = 0

    or

    (2) Carry out the multiplication (3x-4)(2x+7).

    For (1):

    (3x-4)(2x+7) = 0

    The only way two factors can multiply and give 0 is if one of the two factors is equal to 0.

    So either 3x-4 = 0 or 2x+7 = 0.

    In case 3x-4 = 0 then we get 3x = 4, and then x = 3/4.

    In case 2x+7 = 0 then we get 2x = -7, and then x = -7/2.

    Thus there are two possible values for x, 3/4 and -7/2.

    For (2):

    Using the FOIL method we get:

    6x^2 + 21x - 8x - 28,

    which simplifies to

    6x^2 + 13x - 28.

    (NOTE: on the keyboard, we use x^2 to mean x to the 2nd power, or x-squared.)

    Maybe one of these will help.

  • 1 decade ago

    If you are solving for x then you get two answers. You must first break the problem into:

    3x-4=0

    and

    2x+7=0

    You then solve for X giving you 4/3 and -7/2 respectively.

    It would help to know the context of the question.

    Good luck!

  • Anonymous
    1 decade ago

    first multiply 3x by 2x, then multiply 3x by 7 and add them.

    3x*2x + 3x*7 ---> 6x^2 + 21x

    then add to that -4 times 2x, then -4 times 7

    6x^2 + 21x - 4*2x - 4*7

    6x^2 + 21x - 8x - 28 ---> 6x^2 + 13x - 28

    to solve those you "FOIL" (First outside, Inside Last)

    in variable form, you solve like this:

    if you start with (a+b)(c+d)

    then first multiply a by both things in the 2nd set of parenthases (c and d), then add those two products together (because c and d are added together)

    so you'll have: ac + ad

    then multiply b by both things in the 2nd set of parentheses (c and d), then add those two products to what you already had (ac + ad)

    so you'll have ac + ad + bc + bd

    make sure that if there's anything that can be made simpler, you do it (e.g. if you end up with x^2 + 4x + 7x +2, then make sure you simplify it to x^2 + 11x + 2)

    (you can also research the Distributive Property online, because that's what that's called)

    Source(s): through 9th grade math.
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  • 1 decade ago

    (3x-4)(2x+7)

    Use FOIL to get next step (first, outside, inside, last)

    6x^2 + 21x - 8x - 28

    Next, add like terms

    6x^2 + 13x - 28

    Next, you want to use the quadratic equation which is:

    See : http://mathworld.wolfram.com/images/equations/Quad...

    You will use A = 6, B=13, and C= -18

    Source(s): Math major in college
  • Anonymous
    1 decade ago

    3x-4 is -12. 2x+7 is the same as 2x7 which is 14. and the way this is set out is all wrong it should say (3x-4)+(2x7) which is 2. because a negative number plus a positive number means that the negative goes up. eg -4+7=3.

    Source(s): My maths teacher
  • 1 decade ago

    FOIL (first, outer, inner, last)

    (3x-4)(2x+7)

    6x^2 + 21x - 6x -28

    F 0 I L

    6x^2-13x-28 is the answer! Good luck!

    Source(s): Math teacher :)
  • 1 decade ago

    (3x-4)=0 (2x+7)=0

    3x=4 2x=-7

    x=4/3 or x=-7/2

  • 1 decade ago

    is the qns incomplete?

    u wanna solve x?

    all i got was

    6x(squared) + 21x - 8 x - 21= 6x(squared) +13x -21...

  • 1 decade ago

    loren, clooney and happy are the only ones to get this right.

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