He made a mistake in step #2. It seemed to be a trivial mistake because it involved signs, but it still had a great impact. Since step#2, his solution was already wrong.

Instead of
(-1)²-4(2)(-6) = 1 + 48 = 49

What he did is
(-1)²-4(2)(-6) = -1 + 48 = 47

4 0

3 years ago

I need help on this problem in math

S_A_V [24]

Answer:

correct answer is C
Haley incorrectly applied the distributive property

Step-by-step explanation:

If you simplify the given equation, you find it matches choice C.

$\dfrac{1}{2}(6-x)+3x=\dfrac{1}{2}x-8\\\\3-\dfrac{1}{2}x+3x=\dfrac{1}{2}x-8\\\\3+\dfrac{5}{2}x=\dfrac{1}{2}x-8\qquad\text{matches choice C}$

Haley's error seems to be failing to distribute the 1/2 properly when she eliminated parentheses. Apparent, she incorrectly decided that ...

1/2(6 -x) ⇒ 3 -x . . . . instead of 3 -1/2x

Then when -x was added to +3x, she got 2x. Had she done it properly, she would have added -1/2x to +3x to get 5/2x.

_____

Additional comment

It is a common error to "distribute" the factor outside parentheses to the first term only, as Haley apparently did. Another common error is to fail to distribute minus signs properly. The distributive property requires you apply the outside factor to all of the terms inside parentheses.

5 0

2 years ago