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3 years ago

Solve each system of equations by substitution X + 3y = 6 -x + y = -7

Mathematics

1 answer:

notka56 [123]3 years ago

4 0

Answer:

$x = 6.75$

$y = -0.25$

Step-by-step explanation:

Given :

$x + 3y = 6$ ..................... equation 1

$-x + y = -7$ ................... equation 2

solving the system of equation by substitution method , from equation 1 , make x the subject of the formula , that is

$x = 6 - 3y$ ........................... equation 3

substitute equation 3 into equation 2 , that is

$- ( 6 - 3y) + y = -7$

$-6 + 3y + y = - 7$

$-6 + 4y = -7$

$4y = -7 + 6$

$4y = -1$

$y = \frac{-1}{4}$ $= -0.25$

substitute $y = \frac{-1}{4}$ into equation 3 to find the value of x , that is

$x = 6 - 3 (\frac{-1}{4})$

$x = 6 + \frac{3}{4}$

$x = \frac{27}{4}$

$x = 6. 75$

Therefore :

$x = 6. 75$

$y = - 0.25$

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Please help ! 20 pts please

Ksenya-84 [330]

The given ratios expresses the number of time a value is larger or smaller

than another value.

The correct responses are;

3. (B) 12 and 24

4. (D) 6, 9, 21

5. $\underline{(E) \ \displaystyle \frac{11}{2}}$

6. $\underline{(E) \ \displaystyle \frac{5}{14}}$

7. (B) $\overline{EF}$ = 6, $\overline{AC}$ = 9·√5

8. (C) The values are equal

9. (A) The value in column A is greater

Reasons:

3. Given that the perimeter of the rectangle = 72

The ratio of the lengths of the sides = 1:2

Let a and b represent the sides, we have;

2·a + 2·b = 72

$\displaystyle \frac{a}{b} = \mathbf{\frac{1}{2}}$

Which gives;

2·a = b

2·a + 2·(2·a) = 72

6·a = 72

a = 72 ÷ 6 = 12

b = 2·a = 2 × 12 = 24

The lengths of the sides are; (B) 12 and 24

4. Extended ratio = 2:3:7

The perimeter = 36

The lengths of the sides are;

$\displaystyle \frac{2}{2 + 3 + 7} \times 36 = \mathbf{6}$

$\displaystyle \frac{3}{2 + 3 + 7} \times 36 = \mathbf{9}$

$\displaystyle \frac{7}{2 + 3 + 7} \times 36 = \mathbf{21}$

The lengths are; (D) 6, 9, 21

5. The given equation is presented as follows;

$\displaystyle \frac{5}{x + 7} = \mathbf{\frac{3}{x + 2}}$

5 × (x + 2) = 3 × (x + 7)

5·x + 10 = 3·x + 21

5·x - 3·x = 21 - 10

2·x = 11

$\displaystyle x = \mathbf{ \frac{11}{2}}$

The correct option is; $\displaystyle \underline{(E) \ \frac{11}{2}}$

6. The width to length ratio is $\displaystyle \mathbf{\frac{2.5}{7.0}}$

The simplified ratio is therefore;

$\displaystyle \frac{2.5}{7.0} = \frac{2 \times 2.5}{2 \times 7.0} = \mathbf{\frac{5}{14}}$

The correct option is (E) $\displaystyle \underline{(E) \ \frac{5}{14}}$

7. The given ratio of the lengths is 3:1

Therefore;

$\overline{BC}$ : $\overline{EF}$ = 3:1

Which gives;

$\displaystyle \mathbf{\frac{\overline{BC}}{\overline{EF}}} = \frac{3}{1}$

$\overline{BC}$ = 18

Therefore;

$\displaystyle \frac{18}{\overline{EF}} = \frac{3}{1}$

18 × 1 = 3 × $\overline{EF}$

$\displaystyle \overline{EF} = \frac{18 \times 1}{3} = 6$

$\overline{EF}$ = 6

By Pythagorean theorem, we have;

$\overline{DF}$ ² = $\mathbf{\overline{DE}}$ ² + $\mathbf{\overline{EF}}$ ²

Which gives;

$\overline{DF}$ ² = 3² + 6² = 45

$\overline{DF}$ = √(45) = 3·√5

Using the given ratio, we have;

$\overline{AC}$ = 3 × $\mathbf{\overline{DF}}$

Which gives;

$\overline{AC}$ = 3 × 3·√5 = 9·√5

$\overline{AC}$ = 9·√5

The correct option is; (B) $\overline{EF}$ = 6, $\overline{AC}$ = 9·√5

8. EF = 1, AB = 2

CD = 2, CE = 4

Therefore;

$\displaystyle \mathbf{\frac{EF}{AB}} =\frac{1}{2}$

$\displaystyle \mathbf{\frac{CD}{CE}} =\frac{2}{4} = \frac{1}{2}$

Which gives;

$\displaystyle \frac{EF}{AB} =\displaystyle \mathbf{\frac{CD}{CE}}$

(C) The values are equal

9. AC = 6, BE = 8

DF = 3, BD = 6

Column A

$\displaystyle \frac{AC}{BE} =\displaystyle \mathbf{\frac{6}{8}} = \frac{3}{4}$

Column B

$\displaystyle \frac{DF}{BD} =\displaystyle \mathbf{\frac{3}{6}} = \frac{1}{2}$

$\displaystyle \frac{3}{4} > \mathbf{\frac{1}{2}}$

Therefore;

Column A is greater than column B

(A) The value in column A is greater

Learn more about ratios here:

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mike and kim invest $14,000 in equipment to print yearbooks for schools. each yearbook costs $7 to print and sells for $35. how

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The answer is A.) 500 Year books.

The profit they would gain from each year book would be $28 since each year book costs $7 to make and sells for $35. You would simply divide 14,000 by 28 to find how many books they would need to sell in order to get their investment back which would be 500 books.

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Answer:

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