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222-9+11+12:2*14+14 = ? ( )

Toán Lớp 7: tính tổng f(x) + g(x) và hiệu f(x) – g(x) với a) f(x)=10x^5-8x^4 + 6x^3-4x^2+2x+1+3x^6 g(x) = -5x^5+2x^4-4x^3+6x^2-8x+10+2x^6 b)f(x) =

Toán Lớp 7: tính tổng f(x) + g(x) và hiệu f(x) – g(x) với
a) f(x)=10x^5-8x^4 + 6x^3-4x^2+2x+1+3x^6
g(x) = -5x^5+2x^4-4x^3+6x^2-8x+10+2x^6
b)f(x) = 15x^3+7x^2+3x-1/2+3x^4
g(x)=-15x^3-7x^2-3x+1/2+2x^4

Comments ( 2 )

  1. Giải đáp:
    a) f(x)+g(x)=5x^6+5x^5-6x^4+2x^3+2x^2-6x+11
         f(x)-g(x)=x^6+15x^5-10x^4+10x^3-10x^2+10x-9
    b) f(x)+g(x)=5x^4
         f(x)-g(x)==x^4+30x^3+14x^2+6x^3-1
    Lời giải và giải thích chi tiết:
    a) Có f(x)=3x^6+10x^5-8x^4+6x^3-4x^2+2x+1
               g(x)=2x^6-5x^5+2x^4-4x^3+6x^2-8x+10
    f(x)+g(x)
    =(10x^5-8x^4+6x^3-4x^2+2x+1+3x^6)+(-5x^5+2x^4-4x^3+6x^2-8x+10+2x^6)
    =3x^6+10x^5-8x^4+6x^3-4x^2+2x+1+2x^6-5x^5+2x^4-4x^3+6x^2-8x+10
    =(3x^6+2x^6)+(10x^5-5x^5)+(2x^4-8x^4)+(6x^3-4x^3)+(6x^2-4x^2)+(2x-8x)+(1+10)
    =5x^6+5x^5-6x^4+2x^3+2x^2-6x+11
    f(x)-g(x)
    =(3x^6+10x^5-8x^4+6x^3-4x^2+2x+1)-(2x^6-5x^5+2x^4-4x^3+6x^2-8x+10)
    =3x^6+10x^5-8x^4+6x^3-4x^2+2x+1-2x^6+5x^5-2x^4+4x^3-6x^2+8x-10
    =(3x^6-2x^6)+(10x^5+5x^5)+(-8x^4-2x^4)+(6x^3+4x^3)+(-4x^2-6x^2)+(2x+8x)+(1-10)
    =x^6+15x^5-10x^4+10x^3-10x^2+10x-9
    b) Có f(x)=3x^4+15x^3+7x^2+3x-1/2
              g(x)=2x^4-15x^3-7x^2-3x+1/2
    f(x)+g(x)
    =(3x^4+15x^3+7x^2+3x-1/2)+(2x^4-15x^3-7x^2-3x+1/2)
    =3x^4+15x^3+7x^2+3x-1/2+2x^4-15x^3-7x^2-3x+1/2
    =(3x^4+2x^4)+(15x^3-15x^3)+(7x^2-7x^2)+(3x-3x)+(1/2-1/2)
    =5x^4
    f(x)-g(x)
    =(3x^4+15x^3+7x^2+3x-1/2)-(2x^4-15x^3-7x^2-3x+1/2)
    =3x^4+15x^3+7x^2+3x-1/2-2x^4+15x^3+7x^2+3x-1/2
    =(3x^4-2x^4)+(15x^3+15x^3)+(7x^2+7x^2)+(3x+3x)+(-1/2-1/2)
    =x^4+30x^3+14x^2+6x^3-1

  2. ***Lời giải***
    a)
    f(x)=10x^5-8x^4 + 6x^3-4x^2+2x+1+3x^6
    =3x^6+10x^5-8x^4 + 6x^3-4x^2+2x+1
    g(x) = -5x^5+2x^4-4x^3+6x^2-8x+10+2x^6
    =2x^6-5x^5+2x^4-4x^3+6x^2-8x+10
    f(x) + g(x)=3x^6+10x^5-8x^4 + 6x^3-4x^2+2x+1+2x^6-5x^5+2x^4-4x^3+6x^2-8x+10
    f(x) + g(x)=(3x^6+2x^6)+(10x^5-5x^5)+(2x^4-8x^4 )+( 6x^3-4x^3)+(6x^2-4x^2)+(2x-8x)+(1+10)
    f(x) + g(x)=5x^6+5x^5-6x^4+2x^3+2x^2-6x+11
    f(x) – g(x)=3x^6+10x^5-8x^4 + 6x^3-4x^2+2x+1-(2x^6-5x^5+2x^4-4x^3+6x^2-8x+10)
    f(x) – g(x)=(3x^6-2x^6)+(10x^5+5x^5)+(-8x^4-2x^4)+(6x^3+4x^3)+(-4x^2-6x^2)+(2x+8x)+(1-10)
    f(x) – g(x)=x^6+15x^5-10x^4+10x^3-10x^2+10x-9
    b)
    f(x) = 15x^3+7x^2+3x-1/2+3x^4
    =3x^4+15x^3+7x^2+3x-1/2
    g(x)=-15x^3-7x^2-3x+1/2+2x^4
    =2x^4-15x^3-7x^2-3x+1/2
    f(x) + g(x)=3x^4+15x^3+7x^2+3x-1/2+2x^4-15x^3-7x^2-3x+1/2
    f(x) + g(x)=(3x^4+2x^4)+(15x^3-15x^3)+(7x^2-7x^2)+(3x-3x)+(-1/2+1/2)
    f(x) + g(x)=5x^4
    f(x) – g(x)=3x^4+15x^3+7x^2+3x-1/2-(2x^4-15x^3-7x^2-3x+1/2)
    f(x) – g(x)=(3x^4-2x^4)+(15x^3+15x^3)+(7x^2+7x^2)+(3x+3x)+(-1/2-1/2)
    f(x) – g(x)=x^4+30x^3+14x^2+6x-1

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222-9+11+12:2*14+14 = ? ( )