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Lucia finds that (3x^2 + 3x + 5) + (7x^2 - 9x + 8) = 10x^2 - 12x + 13. What error did Lucia make?

A. She found the difference instead of the sum.

B. She combined the terms 3x^2 and 7x^2 incorrectly.

C. She combined the terms 3x and –9x incorrectly.

D. She did not combine all like terms.

Respuesta :

Setor9
The answer is C. The middle term should be -6 and not -12.

Answer:

The correct answer is option C.

Step-by-step explanation:

[tex](3x^2 + 3x + 5) + (7x^2 - 9x + 8) = 10x^2 - 12x + 13[/tex]

[tex]3x^2 + 3x + 5 + 7x^2 - 9x + 8= 10x^2 - 12x + 13[/tex]

[tex]x^2(3+7)+x(3-9)+5+8= 10x^2 - 12x + 13[/tex]

[tex]10x^2-6x-13=10x^2 - 12x + 13[/tex] (wrong)

[tex]10x^2-6x-13\neq 10x^2 - 12x + 13[/tex]

Error made by Lucia was that she added coefficient of x. She must be subtracting those coefficients.

Hence,the correct answer is option C.

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