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EmmaH

  • 3 years ago

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..

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  1. JayDS
    • 3 years ago
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    Do you know the crab claw/Foil method to expand out the brackets?

  2. ZeHanz
    • 3 years ago
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    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!

  3. precal
    • 3 years ago
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    this is a difference of squares as ZeHanz stated

  4. JayDS
    • 3 years ago
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    yes it is indeed but she can easily get the answer if she expands the brackets and collect like terms as well.

  5. EmmaH
    • 3 years ago
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    ii got the answer usinmg foil which is 9a^2+ (-121)

  6. ZeHanz
    • 3 years ago
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    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...

  7. EmmaH
    • 3 years ago
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    but my answermy answer possiblities are 9a2 - 22 9a2 - 121 9a2 + 121 9a2 - 66a + 121

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

  9. JayDS
    • 3 years ago
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    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.

  10. EmmaH
    • 3 years ago
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    thank you peoples!

  11. ZeHanz
    • 3 years ago
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    Welcome!

  12. precal
    • 3 years ago
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    never use double signs|dw:1359206802362:dw|

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