Math  /  Algebra

Question13. Modélise cette soustraction (3x2+4x)(2x2x)\left(-3 x^{2}+4 x\right)-\left(-2 x^{2}-x\right) à l'aide d'un schéma.

Studdy Solution

STEP 1

What is this asking? We need to subtract two expressions, which are groups of terms with xx and x2x^2, and model this subtraction visually! Watch out! Be super careful with those minus signs; they can be tricky!
Double negatives can turn into positives, so keep your eyes peeled!

STEP 2

1. Rewrite the expression
2. Distribute the negative sign
3. Combine like terms

STEP 3

Alright, let's **rewrite** this subtraction problem to make it easier to work with.
We have (3x2+4x)(2x2x)\left(-3 x^{2}+4 x\right)-\left(-2 x^{2}-x\right).
Remember, subtracting a quantity is the same as *adding* its opposite.

STEP 4

So, we can **rewrite** our expression as (3x2+4x)+((2x2x))\left(-3 x^{2}+4 x\right) + \left(-\left(-2 x^{2}-x\right)\right).
We're basically saying, "Instead of subtracting this whole thing, let's add the *opposite* of this whole thing."

STEP 5

Now, let's **distribute** that negative sign into the second set of parentheses.
This means we multiply each term inside the parentheses by 1-1.

STEP 6

So, 12x2-1 \cdot -2x^2 becomes +2x2+2x^2 and 1x-1 \cdot -x becomes +x+x.
See how those double negatives become positives?
Our expression is now (3x2+4x)+(2x2+x)\left(-3 x^{2}+4 x\right) + \left(2 x^{2}+x\right).

STEP 7

Time to **combine** those **like terms**!
Like terms are terms that have the same variable raised to the same power.
We've got x2x^2 terms and xx terms.

STEP 8

Let's **group** our like terms: (3x2+2x2)+(4x+x)(-3x^2 + 2x^2) + (4x + x).

STEP 9

Now, let's **add** the coefficients of the x2x^2 terms: 3+2=1-3 + 2 = -1.
So, we have 1x2-1x^2, or simply x2-x^2.

STEP 10

Next, let's **add** the coefficients of the xx terms: 4+1=54 + 1 = 5.
So, we have 5x5x.

STEP 11

Putting it all together, our **simplified expression** is x2+5x-x^{2}+5 x.
Boom!

STEP 12

The simplified expression representing the subtraction (3x2+4x)(2x2x)\left(-3 x^{2}+4 x\right)-\left(-2 x^{2}-x\right) is x2+5x-x^2 + 5x.

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