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3 years ago

(1 - 7x)(1 + 9x) answers??

Mathematics

2 answers:

Oxana [17]3 years ago

5 0

Answer:

(1 - 7x)(1 + 9x) = -63x² + 2x + 1

Step-by-step explanation:

We have to solve:

(1 - 7x)(1 + 9x)

(1 - 7x)(1 + 9x) = 1(1+9x) -7x(1+9x)

= 1+9x-7x-7x×9x (on distributing 1 and -7x)

= 1+9x-7x-63x²

= -63x² + 2x + 1 (on combining the like terms)

Hence, (1 - 7x)(1 + 9x) = -63x² + 2x + 1

mojhsa [17]3 years ago

3 0

Lets get started :)

( 1 - 7x )( 1 + 9x )
Let us distribute

1 ( 1 ) + 1 ( 9x ) - 7x ( 1 ) - ( 7x )( 9x )
1 + 9x - 7x - 63x²

1 + 2x - 63x²

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3 years ago

The circumference of a sphere was measured to be 80 cm with a possible error of 0.5 cm. A) Use differentials to estimate the max

siniylev [52]

Answer:

A) The maximum error in the calculated surface area: $25cm^2$

Relative error: $0.013$

B) The maximum error in the calculated volume: $162cm^2$

Relative error: $0.019$

Step-by-step explanation:

A) The formula for the surface area is:

$A=4\pi r^2$

The measured value is the circumference which is equal to:

$C=2\pi r$

then the radius is:

$r=\frac{C}{2\pi}$

Substituting in the formula of the surface:

$A=4\pi(\frac{C}{2\pi})^2\\A=4\pi(\frac{C^2}{4\pi^2})\\A=\frac{C^2}{\pi}$

Using the formula to calculate the error:

$dy=f'(x)dx$

Where $x$ is the variable measured and $y$ is a function of $x$ ( $y=f(x)$ ).

$dA=f'(C)dC\\dA=\frac{2C^{(2-1)}}{\pi}dC\\dA=\frac{2C}{\pi}dC$

We have C=80cm and dC=0.5cm

$dA=\frac{2C}{\pi}dC\\dA=\frac{2(80)}{\pi}(0.5)\\dA=\frac{160}{\pi}(0.5)\\dA=50.9296(0.5)\\dA=25.4648\approx25cm^2$

The relative error is the maximum error divide by the total area. The total area is: $A=\frac{C^2}{\pi}=\frac{(80)^2}{\pi}=\frac{6400}{\pi}=2037.1833cm^2$

$\frac{dA}{A}=\frac{25.4648}{2037.1833} =0.0125\approx0.013$

B) The formula for the volume is:

$V=\frac{4}{3} \pi r^3$

Using $r=\frac{C}{2\pi}$

$V=\frac{4}{3} \pi r^3\\V=\frac{4}{3} \pi (\frac{C}{2\pi})^3\\V=\frac{4}{3} \pi (\frac{C^3}{8\pi^3})\\V=\frac{1}{3}(\frac{C^3}{2\pi^2})\\V=\frac{C^3}{6\pi^2}$

The maximum error is:

$dV=\frac{3C^{3-1}}{6\pi^2}dC\\dV=\frac{C^{2}}{2\pi^2}dC\\dV=\frac{(80)^{2}}{2\pi^2}(0.5)\\dV=\frac{6400}{2\pi^2}(0.5)\\dV=\frac{6400}{2\pi^2}(0.5)\\dV=(324.2278)(0.5)\\dV=162.1139\approx162cm^2$

The calculated volume is:

$V=\frac{C^3}{6\pi^2}\\V=\frac{(80)^3}{6\pi^2}\\V=\frac{512000}{6\pi^2}\\V=8646.0743$

The relative error is:

$\frac{dV}{V}=\frac{162.1139}{8646.0743}=0.0188\approx0.019$

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3 years ago

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topjm [15]

Answer:

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Step-by-step explanation:

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Slope of the line passing through two points $(x_{1},y_{1})$ and $(x_{2},y_{2})$ is given as:

$m=(y_{2} -y_{1})/ (x_{2} -x_{1})$

Here, $(x_{1},y_{1})$ and $(x_{2},y_{2})$ are $(-1,4)$ and $(1,-2)$ .

Therefore, slope is equal to, $m=(-2-4 )/ (1-(-1)$

$m=-6/2$

$m=-3$

Now, equation of a straight line with slope m and points $(x_{1},y_{1})$ and $(x_{2},y_{2})$ is given as:

$y-y_{1}=m(x-x_{1})\\y-y_{2}=m(x-x_{2})$

Now, if we use the 2nd form, then $x_{2}=1,y_{2}=-2$ .

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3 years ago