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the volume of a rectangular solid is given by expressions given below.in each case find the dimentions of the solid.

a)15x^2-51x+18.

b)x^3+13x^2+32x+20.

c)x^2-5x/2-3/2.

d)x^4+x^3-x-1

plz everyone help me out.till 2 o'clock...plz plz plz

• math -

Factorize:
a)15x^2-51x+18.
=15x^2-45x -6x+18
=15x(x-3) - 6(x-3)
=(15x-6)(x-3)

b) x^3+13x^2+32x+20.
Notice that by changing the sign of odd powers, the coefficients add up to zero:
-1+13-32+20=0
So x+1 is a factor.
Divide by x+1 gives
x^2+12x+20
(x+2)(x+10)
So the whole factorization is:
(x+1)(x+2)(x+10)

(c) x^2-5x/2-3/2.
=(1/2)(2x^2-5x-3)
=(1/2)[2x^2+x - 3(2x+1)]
=(1/2)[x(2x+1)-3(2x+1)]
=(1/2)(x-3)(2x+1)

(d) will be left as a practice for you.

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