# pretty pls help me gcse maths

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when helen expands (ax+b)^3, she gets the coefficient of x to be 441 and the coefficient of x^2 to be 189. find the value of a/b.

i've expanded it to get:

a^3x^3 + 3a^2x^2b + 3axb^2 + b^3

i've ignored the first and last terms as they don't have x or x^2. i saw a 4 year old thread for this question so i made a new one, but i saw on that forum they did 3ab^2 = 441 and 3a^b = 189. i get that it is something to do with the coefficients of x, but could somebody explain why it is 3ab^2 = 441 and 3a^b = 189? i understand the rest of the process, except that part.

thanks

i've expanded it to get:

a^3x^3 + 3a^2x^2b + 3axb^2 + b^3

i've ignored the first and last terms as they don't have x or x^2. i saw a 4 year old thread for this question so i made a new one, but i saw on that forum they did 3ab^2 = 441 and 3a^b = 189. i get that it is something to do with the coefficients of x, but could somebody explain why it is 3ab^2 = 441 and 3a^b = 189? i understand the rest of the process, except that part.

thanks

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(Original post by

when helen expands (ax+b)^3, she gets the coefficient of x to be 441 and the coefficient of x^2 to be 189. find the value of a/b.

i've expanded it to get:

a^3x^3 + 3a^2x^2b + 3axb^2 + b^3

i've ignored the first and last terms as they don't have x or x^2. i saw a 4 year old thread for this question so i made a new one, but i saw on that forum they did 3ab^2 = 441 and 3a^b = 189. i get that it is something to do with the coefficients of x, but could somebody explain why it is 3ab^2 = 441 and 3a^b = 189? i understand the rest of the process, except that part.

thanks

**uglyplushy**)when helen expands (ax+b)^3, she gets the coefficient of x to be 441 and the coefficient of x^2 to be 189. find the value of a/b.

i've expanded it to get:

a^3x^3 + 3a^2x^2b + 3axb^2 + b^3

i've ignored the first and last terms as they don't have x or x^2. i saw a 4 year old thread for this question so i made a new one, but i saw on that forum they did 3ab^2 = 441 and 3a^b = 189. i get that it is something to do with the coefficients of x, but could somebody explain why it is 3ab^2 = 441 and 3a^b = 189? i understand the rest of the process, except that part.

thanks

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#3

A coefficient is a

So question is telling you the coefficient is

However from the expansion we know the

Therefore these values must be

Cancel the x's and you get 3ab^2 = 441

**number**or symbol multiplied with a variable or an unknown quantity in an**algebraic term**.So question is telling you the coefficient is

**number**is 441 and**algebraic term**is x.However from the expansion we know the

**coefficient of x**is 3ab^2.Therefore these values must be

**equal**so this can be written as 3ab^2**x**= 441**x**Cancel the x's and you get 3ab^2 = 441

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#4

**uglyplushy**)

when helen expands (ax+b)^3, she gets the coefficient of x to be 441 and the coefficient of x^2 to be 189. find the value of a/b.

i've expanded it to get:

a^3x^3 + 3a^2x^2b + 3axb^2 + b^3

i've ignored the first and last terms as they don't have x or x^2. i saw a 4 year old thread for this question so i made a new one, but i saw on that forum they did 3ab^2 = 441 and 3a^b = 189. i get that it is something to do with the coefficients of x, but could somebody explain why it is 3ab^2 = 441 and 3a^b = 189? i understand the rest of the process, except that part.

thanks

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reply

(Original post by

A coefficient is a

So question is telling you the coefficient is

However from the expansion we know the

Therefore these values must be

Cancel the x's and you get 3ab^2 = 441

**Dominininc**)A coefficient is a

**number**or symbol multiplied with a variable or an unknown quantity in an**algebraic term**.So question is telling you the coefficient is

**number**is 441 and**algebraic term**is x.However from the expansion we know the

**coefficient of x**is 3ab^2.Therefore these values must be

**equal**so this can be written as 3ab^2**x**= 441**x**Cancel the x's and you get 3ab^2 = 441

(Original post by

In your expansion, the coefficient of x is . You're told the coeff. of x is 441. Hence they're equal. And in a similar manner x^2

**ghostwalker**)In your expansion, the coefficient of x is . You're told the coeff. of x is 441. Hence they're equal. And in a similar manner x^2

(Original post by

They factorised the x^2 and x terms from 3a^2x^2b and 3axb^2 respectively.

**0ptics**)They factorised the x^2 and x terms from 3a^2x^2b and 3axb^2 respectively.

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