Question

Multiply: (3a + 11)(3a - 11).
9a2 - 22
9a2 - 121
9a2 + 121
9a2 - 66a + 121

i know its either b or c but i donmt knwo which it is..

Answer 1

Do you know the crab claw/Foil method to expand out the brackets?

Answer 2

This is the form: (a-b)(a+b) = a²-b².
It pays to learn this form by heart, so you can recognise them immediately when you see one!

Answer 3

this is a difference of squares as ZeHanz stated

Answer 4

yes it is indeed but she can easily get the answer if she expands the brackets and collect like terms as well.

Answer 5

ii got the answer usinmg foil which is 9a^2+ (-121)

Answer 6

FOILing is fine! It's just that in SOME cases, you don't need it, because you can see the answer right away.
This is such a special case.

Another one: (3p+4q)(3p-4q).

See: sum and difference of the same two numbers,
so the answer is (3p)²-(4q)²=9p²-16q².

You can save so much (spare) time with this...

Answer 7

but my answermy answer possiblities are 9a2 - 22
9a2 - 121
9a2 + 121
9a2 - 66a + 121

Answer 8

The answer you got from FOILING is correct, 9a^2+ (-121).
but one thing, you forgot that + - becomes -
9a^2 -121

Answer 9

Also note for special cases as these u should learn them, so u are able to identify them straight away just as @ZeHanz shows it.

Answer 10

thank you peoples!

Answer 11

Welcome!

Answer 12

never use double signs