When I expand (2x + 7)(x - 1), I get 2x^2 + 5x - 7.

I can use my calculator to help me check if my answer is correct.

For instance, if x = 2,

(2x + 7)(x - 1) = 11

and

2x^2 + 5x - 7 = 11

That means I have done my expansion correctly.

I can safely say, I can do this with any value of x and for any given expression.

Do you agree? Justify your argument with example(s).

No. If x is 0 and if is something/x it would be undefined.

ReplyDeleteNo. if x=3

ReplyDelete2(x)^2+5x-7=2(3)^2+5(3)-7=26

No. x may be 0 (highly unlikely) and then it will be wrong

ReplyDeleteI do not agree. It works almost all the time, but if the x is 0, the equation will not work.

ReplyDeleteIt does not apply to all numbers.

ReplyDeleteThis comment has been removed by the author.

ReplyDeleteno if x is 0 or (-2) then it will wrong

ReplyDeleteDose not works with all the number

ReplyDeleteNo. If x = 0 or x = 1/3 or other fractions that cannot be converted into a decimal.

ReplyDeleteNo. There is a chance it might be zero, then the answer will be different.

ReplyDeleteThis comment has been removed by the author.

ReplyDeleteThis comment has been removed by the author.

ReplyDeleteNo, I would not work all the time.

ReplyDeletee.g. Let x be 5.

(2x + 7)(x - 1)=68

2x^2 + 5x - 7=118

If the value of X increases, the value of the equation gets higher. Since ^2 is exponential, that means that 2^2=4, but if you use a bigger number like 3^2=9, it is different.

ReplyDeleteExample:

Assume that X is 4,

2X4^2 + 5X4 - 7 = 45, not 11.

No, I do not agree as x can also be a negative number and

ReplyDeleteFor instance, if x is -2

(2x+7)(x-1)=(-4+7)(-2-1)=3*-3=-9

and

2x^2 + 5x - 7 = 16-10 + -7 = -1

It does not apply all the time when x=3

ReplyDeleteI do not agree as all the other values cannot work.

ReplyDeleteNO. Example, if the question is x/x-5 - 3/x+7, and the value of x is 5, the denominator would be 0, and the calculator would have an error.

ReplyDelete(stated by ms loh xD)

Let x = 11

ReplyDelete2(x)^2+5(x)-7

= 2(11)^2+5(11)-7

= 22^2+55-7

= 484+55-7

= 534

:O

It works with all whole numbers except for 5 and 0.

ReplyDelete