Question

a cuboid with a volume of 924 cm3 has dimensions 4cm (x+1)cm and (x+11)cm. show clearly that x^2 +12x-220=0. show the equation by factorisation. State both values of x. and finally find the dimensions of the cubiod.

Answer 1

Answer:

4cm, 11cm, 21cm

Step-by-step explanation:

4(x + 1)(x + 11)

4(x ^ 2 + 12x + 44)

x ^ 2 + 12x + 11 = 231

x ^ 2 + 12x + 11 - 231 = 0

x ^ 2 + 12x - 220 = 0

(x - 10)(x + 22) = 0

x = 10 and x = - 22

4cm , 11cm , 21cm

Answer 2

Answer:

Part 1)

The equation by factorization is

$x^{2}+12x-230=(x-(-6+\sqrt{266}))(x-(-6-\sqrt{266}))$

Both values of x are

$x1=-6+\sqrt{266}$

$x2=-6-\sqrt{266}$

Part 2) The dimensions of the cuboid are

$4\ cm$, $(-5+\sqrt{266})\ cm$ and $(5+\sqrt{266})\ cm$

Step-by-step explanation:

step 1

we know that

The volume of the cuboid is equal to

$V=LWH$

substitute the given values

$V=4(x+1)(x+11)$

$V=924\ cm^{3}$

so

$4(x+1)(x+11)=924\\4(x^{2}+11x+x+11)=924\\ 4(x^{2}+12x+11)=924\\x^{2}+12x+11=231\\x^{2}+12x-230=0$

Complete the square

$x^{2}+12x-230=0$

$x^{2}+12x=230$

$x^{2}+12x+36=230+36$

$(x+6)^{2}=266$

square root both sides

$x+6=(+/-)\sqrt{266}$

$x=-6(+/-)\sqrt{266}$

so

$x1=-6+\sqrt{266}$

$x2=-6-\sqrt{266}$

therefore

The equation by factorization is

$x^{2}+12x-230=(x-(-6+\sqrt{266}))(x-(-6-\sqrt{266}))$

step 2

Find the dimensions of the cuboid

The dimensions are

$4\ cm$

$(x+1)\ cm -----> (-6+\sqrt{266}+1)=(-5+\sqrt{266})\ cm$

$(x+11)\ cm ----> (-6+\sqrt{266}+11)=(5+\sqrt{266})\ cm$