Algebra · real student question

Write (98 - 0.18x) times 270 squared in expanded form.

Question

Expand:

(980.18x)2702(98-0.18x)\cdot 270^2

Step-by-step solution

  1. Square the constant first. 270=2710270=27\cdot 10, so

    2702=272102=729100=72900270^2=27^2\cdot 10^2=729\cdot 100=72900

    Pulling the powers of ten out avoids a long multiplication.

  2. Restate as a binomial times a constant.

    (980.18x)2702=(980.18x)72900(98-0.18x)\cdot 270^2=(98-0.18x)\cdot 72900

    Only one distribution is left to do.

  3. Distribute, keeping the sign with its term.

    =98729000.18x72900=98\cdot 72900-0.18x\cdot 72900

  4. Compute the constant term. Use 98=100298=100-2:

    9872900=7290000145800=714420098\cdot 72900=7290000-145800=7144200

  5. Compute the xx coefficient — it comes out whole.

    0.1872900=1872900100=1312200100=131220.18\cdot 72900=\frac{18\cdot 72900}{100}=\frac{1312200}{100}=13122

    Because 7290072900 is divisible by 100100, the decimal disappears entirely, so the expansion is 714420013122x7144200-13122x with integer coefficients.

  6. Verify at x=50x=50. Original: (989)72900=8972900=6488100(98-9)\cdot 72900=89\cdot 72900=6488100. Expansion: 71442001312250=7144200656100=64881007144200-13122\cdot 50=7144200-656100=6488100. The two agree, confirming the result.

Answer

(980.18x)2702=714420013122x(98-0.18x)\cdot 270^2=7144200-13122x

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