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? 發問於 教育及參考書教學 · 10 年前

Maths Question

When a polynomial P(x) is divided by x+1 and x+2, the remainders are -7 and -25 respectively. Find the remainder when P(x) is divided by (x+1)(x+2).

1 個解答

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  • 10 年前
    最愛解答

    By remainder theorem,

    since polynomial P(x) is divided by x+1 , remainder is -7.

    so P(-1) = -7

    since polynomial P(x) is divided by x+2, remainder is -25.

    so P(-2) = -25

    Let P(x) = (x+1)(x+2) Q(x) + R(x) , where Q(x) is the quotient and R(x) is the remainder.

    since P(x) is divided by (x+1)(x+2), deg [(x+1)(x+2)] = 2 , so deg [R(x)] < 2,

    Hence, let R(x) = ax + b,

    since P(-1) = (-1+1)(-1+2) Q(x) + a(-1) + b = -a + b = -7

    and P(-2) = (-2+1)(-2+2) Q(x) + a(-2) + b = -2a + b = -25

    so, a = 18, b = 11,

    R(x) = 18x + 11,

    i.e. the remainder is 18x + 11.

    希望幫到你 :)

    資料來源: me
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