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Ymorist [56]
3 years ago
14

Find the inverse of this matrix. 1 -1 -1 -1 2 3 1 1 4

Mathematics
1 answer:
zheka24 [161]3 years ago
3 0

Let's use Gaussian elimination. Consider the augmented matrix,

\left[\begin{array}{ccc|ccc}1 & -1 & -1 & 1 & 0 & 0\\-1 & 2 & 3 & 0 & 1 & 0\\1 & 1 & 4 & 0 & 0 & 1\end{array}\right]

• Add row 1 to row 2, and add -1 (row 1) to row 3:

\left[\begin{array}{ccc|ccc}1 & -1 & -1 & 1 & 0 & 0\\0 & 1 & 2 & 1 & 1 & 0\\0 & 2 & 5 & -1 & 0 & 1\end{array}\right]

• Add -2 (row 2) to row 3:

\left[\begin{array}{ccc|ccc}1 & -1 & -1 & 1 & 0 & 0\\0 & 1 & 2 & 1 & 1 & 0\\0 & 0 & 1 & -3 & -2 & 1\end{array}\right]

• Add -2 (row 3) to row 2:

\left[\begin{array}{ccc|ccc}1 & -1 & -1 & 1 & 0 & 0\\0 & 1 & 0 & 7 & 5 & -2\\0 & 0 & 1 & -3 & -2 & 1\end{array}\right]

• Add row 2 and row 3 to row 1:

\left[\begin{array}{ccc|ccc}1 & 0 & 0 & 5 & 3 & -1\\0 & 1 & 0 & 7 & 5 & -2\\0 & 0 & 1 & -3 & -2 & 1\end{array}\right]

So the inverse is

\begin{bmatrix}1&-1&-1\\-1&2&3\\1&1&4\end{bmatrix}^{-1} = \boxed{\begin{bmatrix}5&3&-1\\7&5&-2\\-3&-2&1\end{bmatrix}}

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How do you factor 125-x^3?
xz_007 [3.2K]

Step-by-step explanation:

We have

125 - x {}^{3}

First, 125 is a perfect cube because

5 \times 5 \times 5 = 125

and

x^3 is a perfect cube because

x \times  x \times x = x {}^{3}

so we can use the difference of cubes identity

( {x}^{3}  -  {y}^{3} ) = (x - y)( {x}^{2}  + xy +  {y}^{2} )

Let say we have two perfect cubes:

64 because 8×8×8=64

and 27 because 3×3×3=27 and let subtract

64 - 27

we know that

64 - 27 = 37

but using the difference of cubes identity we should get the same thing.

Remeber cube root of 64 is 4 and cube root of 27 is 3 so we have

(4 - 3)( {4}^{2}  + 4(3) + 3 {}^{2} )

1(16 + 12 + 9) = 1(37) = 37

So the difference of cubes works for real numbers. This is a good way to help remeber the identity using real numbers.

Back on to the topic,

we know that 5 is cube root of 125 and x is the cube root of x^3 so we have

(5 - x)( {5}^{2}  + 5x +  {x}^{2} ) =

(5 - x)(25 + 5x +  {x}^{2} )

3 0
2 years ago
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ladessa [460]

Answer:

x^{2}-2+\frac{20}{x+7}

Step-by-step explanation:

x + 7) x³ + 7x²- 2x + 6 ( x²- 2

        <u> x³ + 7x²</u>

                     -2x + 6

                     <u>-2x - 14</u>

                           +20

Therefore, we can write the expression in the remainder quotient form as,

x^{2}-2+\frac{20}{x+7}

5 0
3 years ago
One angle of an isosceles triangle measures 138°. Which other angles could be in that isosceles triangle?
BartSMP [9]

Answer:

2 21 degree angles

Step-by-step explanation:

An isosoles triangle has two congruent angles and every triangle's sum of interior angles equals 180 degrees. 138*2>180, so the 138 degree angle cannot be congruent to any of the other angles. Therefore:

180=138+2x

42=2x

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3 years ago
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Which expression is equivalent to (x^4/3 x^2/3)^1/3?
KATRIN_1 [288]

Answer: x^{\frac{2}{3} }

Step-by-step explanation:

We have several properties of exponents in use here. The two that are used are:

(x^{a})(x^{b}) = x^{a + b} <em>(Exponents with the same base that are being multiplied together can have the exponents added)</em>

(x^{a})^{b} = x^{(a)(b)} <em>(A base raised to a power, and then raised to another power means that you can multiply the exponents to get the same result as doing inside operations and then outside operations)</em>

<em />

Let's apply it!

First, let's simplify what's inside the parenthesis.

x^{\frac{4}{3} } x^{\frac{2}{3} } <em>(Remember, they have the same base of "x", so we can add the exponents)</em>

x^{\frac{4}{3} + \frac{2}{3} } = x^{\frac{6}{3} } = x^{2}

Now we have (x^{2})^{\frac{1}{3} }. Let's use the second rule.

(x^{2})^{\frac{1}{3} } = x^{\frac{2}{3} }

Hope this helps! :^)

7 0
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