How do I solve: 6x^2 -x-12=0 ^2 means squared by the way!

Tammy scored 88, 72, 44 points on her first three test. What must she score in her last test to get at least an average of 70?

lara [203]

Answer:

76

Step-by-step explanation:

(88+72+44+x)/4=70

88+72+44+x=280

204+x=280

x=76

Therefore, Tammy needs to score a 76 on her last test to get at least an average of 70.

5 0

3 years ago

For which system of equations is (5, 3) the solution? A. 3x – 2y = 9 3x + 2y = 14 B. x – y = –2 4x – 3y = 11 C. –2x – y = –13 x

Alla [95]

The correct answer is:

D) $\left \{ {{2x-y=7} \atop {2x+7y=31}} \right.$ .

Explanation:

We solve each system to find the correct answer.

For A:
$\left \{ {{3x-2y=9} \atop {3x+2y=14}} \right.$

Since we have the coefficients of both variables the same, we will use elimination to solve this.

Since the coefficients of y are -2 and 2, we can add the equations to solve, since -2+2=0 and cancels the y variable:
$\left \{ {{3x-2y=9} \atop {+(3x+2y=14)}} \right. 
\\
\\6x=23$

Next we divide both sides by 6:
6x/6 = 23/6
x = 23/6

This is not the x-coordinate of the answer we are looking for, so A is not correct.

For B:
$\left \{ {{x-y=-2} \atop {4x-3y=11}} \right.$

For this equation, it will be easier to isolate a variable and use substitution, since the coefficient of both x and y in the first equation is 1:
x-y=-2

Add y to both sides:
x-y+y=-2+y
x=-2+y

We now substitute this in place of x in the second equation:
4x-3y=11
4(-2+y)-3y=11

Using the distributive property, we have:
4(-2)+4(y)-3y=11
-8+4y-3y=11

Combining like terms, we have:
-8+y=11

Add 8 to each side:
-8+y+8=11+8
y=19

This is not the y-coordinate of the answer we're looking for, so B is not correct.

For C:
Since the coefficient of x in the second equation is 1, we will use substitution again.

x+2y=-11

To isolate x, subtract 2y from each side:
x+2y-2y=-11-2y
x=-11-2y

Now substitute this in place of x in the first equation:
-2x-y=-13
-2(-11-2y)-y=-13

Using the distributive property, we have:
-2(-11)-2(-2y)-y=-13
22+4y-y=-13

Combining like terms:
22+3y=-13

Subtract 22 from each side:
22+3y-22=-13-22
3y=-35

Divide both sides by 3:
3y/3 = -35/3
y = -35/3

This is not the y-coordinate of the answer we're looking for, so C is not correct.

For D:
Since the coefficients of x are the same in each equation, we will use elimination. We have 2x in each equation; to eliminate this, we will subtract, since 2x-2x=0:

$\left \{ {{2x-y=7} \atop {-(2x+7y=31)}} \right. 
\\
\\-8y=-24$

Divide both sides by -8:
-8y/-8 = -24/-8
y=3

The y-coordinate is correct; next we check the x-coordinate Substitute the value for y into the first equation:
2x-y=7
2x-3=7

Add 3 to each side:
2x-3+3=7+3
2x=10

Divide each side by 2:
2x/2=10/2
x=5

This gives us the x- and y-coordinate we need, so D is the correct answer.

7 0

4 years ago

[(21 + 5) ÷ 2] + 7 • (8 - 3) equals

kow [346]

[(21 + 5) ÷ 2] + 7 × (8 - 3)
[26 ÷ 2] + 7 × (8 - 3)
13 + 7 × (8 - 3)
13 + 7 × 5
13 + 35
48

6 0

3 years ago

How do I find the median for 77,82,87,85,32,78?

alisha [4.7K]

Answer:

80

Step-by-step explanation:

The median is the middle value of the data arranged in ascending order. If there is no exact middle then the median is the average of the 2 values either side of the middle

Arrange the data in ascending order ( smallest to largest )

32, 77, 78, 82, 85, 87

There is no value exactly in the middle, use the average

median = $\frac{78+82}{2}$ = $\frac{160}{2}$ = 80

5 0

3 years ago

A bag of rice weighs 3.18 pounds. Find its mass in kilograms. ( 1 kg = 2.2 lb)

jeka57 [31]

Hello! So, to find the mass of the bag of rice in kilograms, you must do 3.18/2.2. 3.18/2.2 is 1.4454 and other numbers or 1.45 when rounded to the nearest hundredth. The bag of rice weighs about 1.45 kilograms.

4 0

4 years ago

How do I solve:6x^2 -x-12=0^2 means squared by the way!