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4 years ago

George and Bella are asked to solve −3x − 30 = 5x + 18. Identify where one of them made an error.

Mathematics

2 answers:

scZoUnD [109]4 years ago

7 0

Answer:

Bella made an error in step 2

Step-by-step explanation:

The given equation is:

-3x-30=5x+18

Rearranging the like terms, we get

⇒-3x-5x=18+30

⇒-8x=48

⇒x=-6

Thus, the correct value of x is -6.

Now, Bella made a mistake in her solution as:

-3x-30=5x+18

⇒−3x − 30 − 3x = 5x + 18 − 3x (she should add 3x on both sides rather than subtracting)

⇒− 30 = 2x + 18

⇒−30 − 18 = 2x + 18 −18

⇒− 48= 2x

⇒x=-24

Anika [276]4 years ago

4 0

For the second,
In the first step, instead of adding 3x for both sides, they subtract 3x instead.

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You are designing a rectangular garden. the garden will be enclosed by fencing on three sides and by a house on the fourth side.

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Suppose the dimensions of the rectangle is x by y and let the side enclosed by a house be one of the sides measuring x, then the sides that is to be enclosed are two sides measuring y and one side measuring x.

Thus, the length of fencing needed is given by

P = x + 2y

The area of the rectangle is given by xy,

i.e.

$xy = 288 \\ \\ \\ \\ \Rightarrow y= \frac{288}{x}$

Substituting for y into the equation for the length of fencing needed, we have

$P=x+2\left( \frac{288}{x} \right)=x+ \frac{576}{x}$

For the amount of fencing to be minimum, then

$\frac{dP}{dx} =0 \\ \\ \Rightarrow1- \frac{576}{x^2} =0 \\ \\ \Rightarrow \frac{576}{x^2} =1 \\ \\ \Rightarrow x^2=576 \\ \\ \Rightarrow x=\sqrt{576}=24$

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