Algebraic rules questions?

how do i evaluate 905^2 - 95^2 using suitable algebraic rules?

what about 38*62+38^2 and 69*45+45*31

4 Answers

Relevance
  • Pranil
    Lv 7
    1 decade ago
    Favorite Answer

    a^2 – b^2 = (a + b)(a – b)

    905^2 – 95^2 = (905 + 95)(905 – 95)

    = 1000 × 810 = 810000

    (a × b) + (a × c) = a(b + c)

    38 × 62+38 × 38

    = 38(62 + 38)

    = 38(100) = 3800

    69 × 45 + 45 × 31

    = 45(69 + 31)

    = 45 × 100 = 4500

  • 1 decade ago

    905^2-95^2 = (905+95)(905-95) = 1000*810 = 810,000

    38*62+38^2 = 38(62+38) = 38(100) = 3,800

    69*45 + 45*31 = 45(69+31) = 45*100 = 4500

  • 1 decade ago

    905^2 - 95^2

    diff of two squares

    (905 - 95)(905+95)

    (810)(1000)=810000

    (38)62+38^2

    (38)(62)+(38)(38)

    (38)(38+62)

    38*100=3800

    69*45 +45*31

    45*(69+31)

    45*100

    4500

  • 1 decade ago

    Not sure I would call that algebra, more like arithmetic, but I suppose you could do something like:

    (905)^2 -95 ^2 -->

    ((1000-95)^2 -95^2 -->

    (1000)^2 -2*(95)(1000) +95^2 -95^2 -->

    I will leave the rest to you :)

    Source(s): Math degree from top university
Still have questions? Get your answers by asking now.