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3 years ago

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If the sum of x and y is 90 and y is 6 more than four times x, which of the following systems of equations could be used to solv

e for x and y?
A.x+y=90
x−4y=6

B.x+y=90
4x−y=−6

C.x+y=90
6x−y=−4

D.x+y=90
4x−y=6

1 answer:

marishachu [46]3 years ago

8 0

Answer:

B

Step-by-step explanation:

x + y =90

y= 4x +6

_______

x + y = 90

4x − y = -6

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Please help i need answer for test

Korvikt [17]

Answer:

He did the complete opposite of what he needed to do

Step-by-step explanation:

The error is that when you need to find x - intercept, you need to replace the value of y with zero, not the y value.

Cause otherwise, what he did here is to find the y - intercept

If you have any questions about the way I solved it, don't hesitate to ask me in the comments below :)

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3 years ago

Prove A-(BnC) = (A-B)U(A-C), explain with an example

NikAS [45]

Answer:

Prove set equality by showing that for any element $x$ , $x \in (A \backslash (B \cap C))$ if and only if $x \in ((A \backslash B) \cup (A \backslash C))$ .

Example:

$A = \lbrace 0,\, 1,\, 2,\, 3 \rbrace$ .

$B = \lbrace0,\, 1 \rbrace$ .

$C = \lbrace0,\, 2 \rbrace$ .

$\begin{aligned} & A \backslash (B \cap C) \\ =\; & \lbrace 0,\, 1,\, 2,\, 3 \rbrace \backslash \lbrace 0 \rbrace \\ =\; & \lbrace 1,\, 2,\, 3 \rbrace \end{aligned}$ .

$\begin{aligned}& (A \backslash B) \cup (A \backslash C) \\ =\; & \lbrace 2,\, 3\rbrace \cup \lbrace 1,\, 3 \rbrace \\ =\; & \lbrace 1,\, 2,\, 3 \rbrace\end{aligned}$ .

Step-by-step explanation:

Proof for $[x \in (A \backslash (B \cap C))] \implies [x \in ((A \backslash B) \cup (A \backslash C))]$ for any element $x$ :

Assume that $x \in (A \backslash (B \cap C))$ . Thus, $x \in A$ and $x \not \in (B \cap C)$ .

Since $x \not \in (B \cap C)$ , either $x \not \in B$ or $x \not \in C$ (or both.)

If $x \not \in B$ , then combined with $x \in A$ , $x \in (A \backslash B)$ .
Similarly, if $x \not \in C$ , then combined with $x \in A$ , $x \in (A \backslash C)$ .

Thus, either $x \in (A \backslash B)$ or $x \in (A \backslash C)$ (or both.)

Therefore, $x \in ((A \backslash B) \cup (A \backslash C))$ as required.

Proof for $[x \in ((A \backslash B) \cup (A \backslash C))] \implies [x \in (A \backslash (B \cap C))]$ :

Assume that $x \in ((A \backslash B) \cup (A \backslash C))$ . Thus, either $x \in (A \backslash B)$ or $x \in (A \backslash C)$ (or both.)

If $x \in (A \backslash B)$ , then $x \in A$ and $x \not \in B$ . Notice that $(x \not \in B) \implies (x \not \in (B \cap C))$ since the contrapositive of that statement, $(x \in (B \cap C)) \implies (x \in B)$ , is true. Therefore, $x \not \in (B \cap C)$ and thus $x \in A \backslash (B \cap C)$ .
Otherwise, if $x \in A \backslash C$ , then $x \in A$ and $x \not \in C$ . Similarly, $x \not \in C \!$ implies $x \not \in (B \cap C)$ . Therefore, $x \in A \backslash (B \cap C)$ .

Either way, $x \in A \backslash (B \cap C)$ .

Therefore, $x \in ((A \backslash B) \cup (A \backslash C))$ implies $x \in A \backslash (B \cap C)$ , as required.

8 0

2 years ago

Russell randomly surveys seventh-graders in his school and finds that 6 of 30 attend summer camp. If there are 200 seventh-grade

Lady_Fox [76]

Answer:

40

Step-by-step explanation:

6 of 30 is the ratio 6 to 30 or 6/30.

6/30 reduces to 1/5

The survey shows that 1/5 of the students attend summer camp.

1/5 of 200 = 1/5 * 200 = 40

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3 years ago

5 times the difference of 29 and a number is 215. Which equation below can be used to find the unknown number?

Verdich [7]

Is it multiple choice? If not I would say 215=5(x)-29

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3 years ago

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A line is drawn so that it passes through the points (-3, -1) and (4, 2).

marusya05 [52]

Answer:

y - 2 3/7 (x-4)

Step-by-step explanation:

A) To find slope, use the equation:where and are the x and y values of one coordinate point , and and are the x and y values of another coordinate point . Since we are given two coordinate points, (-3,-1) and (4,2), that means we can find the slope using the slope equation.

Let's choose (4, 2) as your point and (-3, -1) as your point, but you can switch those if you want! That makes and x^1 = -3, y1 = -1 . Plug these values into the slope equation:

The slope of the line is 3/7.

B) Remember that the general equation for point-slope form is, where m = the slope, = the x value of a coordinate point on the line, and = the y value of the same coordinate point on the line.

You are given (4, 2) as one of the coordinate points. That means = 4 and = 2. We found the slope, m = in part A. Now plug these values into the general equation for point-slope form to find your point-slope form equation:

Your point-slope form equation is y - 2 3/7 (x-4).

4 0

2 years ago

Read 2 more answers