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3 years ago

Solve the quadratic equation by factoring: 15x^2+4x-4=0

1 answer:

7 0

We can factor by grouping. To do so, we multiply the leading coefficient with the constant at the end. In other words, a times c (ax^2 + bx + c).

15*-4 = -60

Now we need to split the b term into two pieces that multiply to -60 and add to 4.

-6 and 10 will work.

Now group one part of b with the 15x^2 and the other part with -4.

(15x^2 + 10x) + (-6x - 4)

Now factor both terms.

5x(3x+2) - 2(3x+2)

3x+2 is one of our factors and 5x-2 is the other.

(3x+2)(5x-2)=0

Now just find the zeros.

3x+2 = 0
3x = -2
x = -2/3

And

5x-2 = 0
5x = 2
x = 2/5

So the answer is x = -2/3 and x = 2/5

You might be interested in

14 lessons costs $210. What would 72 lessons cost

Oksi-84 [34.3K]

Answer:

$1,080

Step-by-step explanation:

To solve, we can make a proportion

14 lessons are $210 and 72 lessons are $x

14/210=72/x

Cross multiply

14*x=210*72

14x=15120

To solve for x, we need to get x by itself. Since x is being multiplied by 14, divide both sides by 14.

14x/14=15120/14

x=1080

So, 72 lessons will cost $1,080

4 0

2 years ago

Read 2 more answers

Complete parallel side 2

Gnoma [55]

Step-by-step explanation:

Assume length of side 2 = L

Area of parallelogram is Height x L

So, 72 = 8 x L

L = 9

8 0

2 years ago

Suppose the sediment density (g/cm3 ) of a randomly selected specimen from a certain region is known to have a mean of 2.80 and

Irina18 [472]

Answer:

0.918 is the probability that the sample average sediment density is at most 3.00

Step-by-step explanation:

We are given the following information in the question:

Mean, μ = 2.80

Standard Deviation, σ = 0.85

Sample size,n = 35

We are given that the distribution of sediment density is a bell shaped distribution that is a normal distribution.

Formula:

$z_{score} = \displaystyle\frac{x-\mu}{\sigma}$

Standard error due to sampling:

$=\dfrac{\sigma}{\sqrt{n}} = \dfrac{0.85}{\sqrt{35}} = 0.1437$

P(sample average sediment density is at most 3.00)

$P( x \leq 3.00) = P( z \leq \displaystyle\frac{3.00 - 2.80}{0.1437}) = P(z \leq 1.3917)$

Calculation the value from standard normal z table, we have,

$P(x \leq 3.00) = 0.918$

0.918 is the probability that the sample average sediment density is at most 3.00

4 0

3 years ago

If the sales tax in your city is 11.4%, and an item costs $160 before tax, how much tax would you pay on that item? Round to the

Oksana_A [137]

First we calculate the tax on the item:
11.4%($160) = 11.4(160)/100 = 18.24
hence the tax for the item is $18.24
The total price for the item would be:
160 + 18.24 = 178.24
hence the total price for the item including tax is:
$<span>178.24</span>

7 0

3 years ago

Help me with this question someone.

shusha [124]

Answer:

Step-by-step explanation:

300 minus 15 ( times each week that passed) would equal how much she owes

4 0

2 years ago