Question

2x^2+11x-21 what is the polynomial for this, AND HOW?? Plz & thx

Answer 1

Use breaking the middle term.

Answer 2

I still don't understand how to solve the problem

Answer 3

Thinking of two digits which add up to 11 and when you multiply them they become -42

Answer 4

@flyqueen I hope your question is correct and there is no sign problem ?

Answer 5

I still don't understand can u solve it in steps for me plzzz and thank u for ur time

Answer 6

I am off to sleep

@sirm3d Please help.

Answer 7

Good nite @hba

Answer 8

factoring problem?

Answer 9

Yea

Answer 10

we'll try hba's method. can you think of two numbers (can be negative) that add up to 11 and whose product is -42?
the product is negative so that means one of the numbers is positive and the other is negative.

Answer 11

Umm I'm not sure what hba was talking about. So I'm kind of confused with thinking of a #

Answer 12

well, the 11 is the coefficient of the middle term, while -42 is the product of the coefficients of the first and last terms.
suppose your number is 7 and (-6). 7(-6) = -42 but 7 + (-6) = 1 \(\neq\) 11. so 7 and (-6) are not the right pair.

Answer 13

can you think of a different number pair that add up to 11 and whose product is -42?

Answer 14

okay, i'll give the numbers, 14 and (-3).
\[\large \begin{equation} 2x^2 +11x-21 \\ \quad = 2x^2+(14-3)x-21\\ \quad = 2x^2 + 14x - 3x - 21 \\ \quad = (2x^2+14x)+(-3x-21) \\\quad = 2x(x+7) -3(x+7) \\\quad = (2x-3)(x+7)\end{equation}\]

Answer 15

@sirm3d
Wouldn't slide and divide be easier?
X^2+11x-42
(X+14)(x-3)
(X+14/2)(x-3/2)(2)
(X-7)(x-3)

Answer 16

Sorry it's: (x+7)(2x-3)

Answer 17

it works for you, so that's all right. but others may not see the trick and get lost in the solution.

Answer 18

Just a suggestion. Slide the coefficient of X and multiply it by the third term then divide the coefficient of x by that product.

Answer 19

Then just do foil to check your answer