If (9x − 4)(9x + 4) = ax2 − b, what is the value of a?
The value of a is _____________.

- anonymous

If (9x − 4)(9x + 4) = ax2 − b, what is the value of a?
The value of a is _____________.

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- schrodinger

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- anonymous

@jim_thompson5910

- jim_thompson5910

hint:
(x-y)*(x+y) = x^2 - y^2

- anonymous

i stoll dont get it im lost as to how u solve these

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## More answers

- jim_thompson5910

has your teacher covered the difference of squares rule in any of the lessons?

- anonymous

im taking an online course so the only explanation for problems we have are written down lessons and it hard for me to learn tht way

- jim_thompson5910

read this article and tell me if it helps or not
http://www.purplemath.com/modules/specfact.htm

- anonymous

ok

- anonymous

not really but if u exokain to me i should pick up quickly

- anonymous

*explain

- jim_thompson5910

have you learned of the FOIL rule at all?

- anonymous

o ok yes

- jim_thompson5910

so you will FOIL out (9x-4)*(9x+4)

- anonymous

u multiply the first outside then inner then last

- jim_thompson5910

yes

- jim_thompson5910

what do you get when you FOIL ?

- anonymous

well wen i did the first terms i got 81 wich feels wrong to me

- jim_thompson5910

it's close, it should be 81x^2

- jim_thompson5910

notice how ax^2 and 81x^2 match up

- anonymous

o ok i know it was x^2 but i was unsure about the 81 part

- jim_thompson5910

ah ok

- anonymous

my bad my mom called me but b1x^2+36x-36x+16?

- jim_thompson5910

you mean 81x^2 + 36x - 36x + 16 right?

- anonymous

yes lol my bad

- jim_thompson5910

what happens with the 36x and the -36x ?

- jim_thompson5910

they combine to what?

- anonymous

cancell out of the equation leaving u with81x^2+16

- jim_thompson5910

oh my bad, the +16 should be -16

- jim_thompson5910

but yes they cancel

- jim_thompson5910

you should get 81x^2 - 16

- anonymous

o yea becuse its a negative four time positive 4

- anonymous

o ok thenw ats next

- jim_thompson5910

compare ax^2 - b with 81x^2 - 16

- anonymous

so its 81?

- jim_thompson5910

a = 81, yes

- anonymous

can u help with more?

- jim_thompson5910

sure, one more

- anonymous

ok thank you

- jim_thompson5910

np

- anonymous

Choose the correct simplification of 8x2(4x + 2x2 − 1).

- jim_thompson5910

when you distributed, what did you get?

- anonymous

WHEN I DISTRIBUTE WAT DO I DO WITH THE ^2 THATS ON THE 8

- jim_thompson5910

you basically multiply 8x^2 by each term inside

- jim_thompson5910

|dw:1438821206787:dw|

- jim_thompson5910

|dw:1438821231018:dw|

- anonymous

FIRST IS 32X^3 THEN 16X^4 THEN -8X^2?

- anonymous

BUT U HAVE TO PUT IT IN STANDARD FORM RIGHT?

- anonymous

?

- jim_thompson5910

good
|dw:1438821424219:dw|

- jim_thompson5910

then yeah, write the terms where the largest exponent comes first, then the next largest and so on

- anonymous

OK I GOT THE ANSWER THANK YOU CAN U HELP WITH ONE MORE ITS A QUICK ONE ITS JUST CONFUSING

- jim_thompson5910

ok

- anonymous

Choose the polynomial written in standard form.
xy2 + 4x4y + 10x2
x4y2 + 4x3y + 10x
x4y2 + 4x3y5 + 10x2
x6y2 + 4x3y8 + 10x

- anonymous

MY BAD LET ME WRITE THEM CORRECTLY

- anonymous

XY^2+4X^4Y+10X^2
X^4Y^2+4X^3Y+10X
X^4Y^2+4X^3Y^5+10X^2
X^6Y^2+4X^3Y^8+10X

- anonymous

I KNOW THEY NEED TO BE IN ORDER BUT NONE OF THEM ARE FROM HIGHEST EXPONENT TO LOWEST

- jim_thompson5910

whenever you have mixed variables like this, you add the exponents for each term
then see if those sums are in descending order

- anonymous

OK SO IS IT B?

- jim_thompson5910

For example, look at choice D
first term is x^6y^2, the sum of the exponents is 6+2 = 8
second term is 4x^3y^8, the sum of the exponents is 3+8 = 11
the sum goes from 8 to 11, which is NOT decreasing, so D is out

- jim_thompson5910

yes the sums of the exponents for choice B are decreasing

- anonymous

OK THANK YOU SO MUCH MAN

- jim_thompson5910

np

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