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2007-03-08 22:09:35 · 7 answers · asked by jack r 1 in Science & Mathematics Mathematics

7 answers

It is pretty cool to see that it is a quadratic equation after all:

Use (x + a)^3 = x^3 + 3ax^2 + 3a^2*x + a^3 with a=7

x^3 + 21x^2 + 147x + 343 = x^3 + 133 // - x^3 + 133

21x^2 + 147x + 210 = 0 // Let's divide it by 21

x^2 + 7x + 10 = 0

Now, I can see without the whole procedrue of solving a quadratic equation that

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

x1 = -2
x2 = -5

2007-03-08 22:18:38 · answer #1 · answered by Amit Y 5 · 0 0

do u mean (x+7)^3 =x^3 + 133?
if so then u will need to expand (x+7)^3 either with the aid of a pascal triangle or using binomial expansion

so (x+7)^3=x^3+3(x^2)*7+3x(7^2)+7^3=x^3+21x^2+147x+343

so we have x^3+21x^2+147x+343=x^3 + 133

so 21x^2+147x+210=0
x^2+7x+10=0
(x+5)(x+2)=o
x=-5 or x=-2

2007-03-09 06:22:55 · answer #2 · answered by hiphop 2 · 0 0

(x+7)^3 =x^3 + 133... three represents cube then this is the solution,

first, get (x+7)^2 which is (x^2+14x+49) multiply this by (x+7) to get (x+7)^3 equals to (x^3+21x^2+147x+343), equate this equation with x^3 + 133

x^3+21x^2+147x+343 = x^3 + 133

In general form, 21x^2+147x+210 = 0
divide this by 21, x^2+7x+10 = 0
by factorization, (x+5)(x+2)=0

x = -5 and -2

2007-03-09 07:06:57 · answer #3 · answered by reddish 3 · 0 0

(x + 7)3 = x3 + 133
distribute
3x + 21 = 3x + 133
there is no solution
reductio ad absurdum

2007-03-09 06:16:47 · answer #4 · answered by Matthew P 4 · 0 0

is it (x+7)* 3 ??

2007-03-09 06:32:18 · answer #5 · answered by sikunj.patel 2 · 0 0

3(x+3)=3x+133
3x+9=3x+133
3x-3x=133-9
x dont exist

2007-03-09 07:25:40 · answer #6 · answered by dj opelac(shs II dalton) 1 · 0 0

first of all you should know what is the value of x then i can answer your question!!

2007-03-09 06:12:48 · answer #7 · answered by Anonymous · 0 0

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