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

Toán Lớp 8: 1, a, 5x^2-3x+x(1-5x)=-3 b, 4x^2-9-(2x-3)(x-4)=0 2, a, $\frac{3xy-17x}{9xy^2}$+$\frac{5xy+17x}{9xy^2}$ b, $\frac{25x^2-8}{5x-1}$+$

Home/ Toán Lớp 8: 1, a, 5x^2-3x+x(1-5x)=-3 b, 4x^2-9-(2x-3)(x-4)=0 2, a, $\frac{3xy-17x}{9xy^2}$+$\frac{5xy+17x}{9xy^2}$ b, $\frac{25x^2-8}{5x-1}$+$

Toán Lớp 8: 1, a, 5x^2-3x+x(1-5x)=-3 b, 4x^2-9-(2x-3)(x-4)=0 2, a, $\frac{3xy-17x}{9xy^2}$+$\frac{5xy+17x}{9xy^2}$ b, $\frac{25x^2-8}{5x-1}$+$

Tháng Tư 5, 2023 Toán học 1 Comment 0 views

Toán Lớp 8: 1,
a, 5x^2-3x+x(1-5x)=-3
b, 4x^2-9-(2x-3)(x-4)=0
2,
a, $\frac{3xy-17x}{9xy^2}$+$\frac{5xy+17x}{9xy^2}$
b, $\frac{25x^2-8}{5x-1}$+$\frac{25-30x}{5-25x}$+$\frac{4-4x}{5x-1}$
c, $\frac{x+1}{x-2}$+$\frac{5-x}{2+x}$+$\frac{9x-2-x^2}{4-x^2}$

Comments ( 1 )

  1. annhocbichchaubich
    annhocbichchaubich
    5 Tháng Tư, 2023 at 8:08 chiều
    Reply
    1,
    a, 5x^2-3x+x(1-5x)=-3
    <=> 5x^2-3x+x-5x^2=-3
    <=> 5x^2-2x-5x^2=-3
    <=> -2x=-3
    <=> x = -3/-2
    <=> x = 3/2 
    Vậy x = 3/2
    b, 4x^2-9-(2x-3)(x-4)=0 
    <=> 4x^2-9-(2x^2-11x+12)=0
    <=> 4x^2-9-2x^2+11x-12=0
    <=> 2x^2-9+11x-12=0
    <=> 2x^2-21+11x=0
    <=> 2x^2+11x-21=0
    <=> (2x^2-3x)+(14x-21)=0
    <=> x(2x-3)+7(2x-3)=0
    <=> (2x-3)(x+7)=0
    <=> \(\left[ \begin{array}{l}2x-3=0\\x=-7\end{array} \right.\) 
    <=> \(\left[ \begin{array}{l}x=\dfrac{3}{2}\\x=-7\end{array} \right.\) 
    Vậy x in {3/2;-7}
    2,
    a, {3xy-17x}/{9xy^2} + {5xy+17x}/{9xy^2}
    = {x(3y-17)}/{9xy^2} + {5xy+17x}/{9xy^2}
    = {3y-17}/{9y^2} + {5xy+17x}/{9xy^2}
    = {3y-17}/{9y^2} + {x(5y+17)}/{9xy^2}
    = {3y-17}/{9y^2} + {5y+17}/{9y^2}
    = {3y-17+5y+17}/{9y^2}
    = {8y}/{9y^2}
    = 8/{9y}
    b, {25x^2-8}/{5x-1} + {25-30x}/{5-25x} + {4-4x}/{5x-1}
    = {25x^2-8}/{5x-1}+{5(-6x+5)}/{5(-5x+1)} + {4-4x}/{5x-1}
    = {25x^2-8}/{5x-1} + {-6x+5}/{-5x+1}+{4-4x}/{5x-1}
    = {25x^2-8}/{5x-1} + {-(-6x+5)}/{5x-1} + {4-4x}/{5x-1}
    = {25x^2-8-(-6x+5)}/{5x-1} + {4-4x}/{5x-1}
    = {25x^2-8+6x-5}/{5x-1} + {4-4x}/{5x-1}
    = {-13+25x^2+6x}/{5x-1}+{4-4x}/{5x-1}
    = {-13+25x^2+6x+4-4x}/{5x-1}
    = {-9+25x^2+2x}/{5x-1} 
    = {25x^2+2x-9}/{5x-1}
    c, {x+1}/{x-2}+{5-x}/{2+x}+{9x-2-x^2}/{4-x^2}
    = {(x+1)(x+2)}/{(x-2)(x+2)} + {(5-x)(x-2)}/{(x-2)(x+2)} + {9x-2-x^2}/{4-x^2}
    = {(x+1)(x+2)+(5-x)(x-2)}/{(x-2)(x+2)} + {9x-2-x^2}/{4-x^2}
    = {x^2 + 2x+2+x+5x-10-x^2+2x}/{(x-2)(x+2)} + {9x-2-x^2}/{4-x^2}
    = {10x-8}/{(x-2)(x+2)} + {9x-2-x^2}/{4-x^2}
    = {10x-8}/{(x-2)(x+2)} + {9x-2-x^2}/{(x-2)(-x-2)}
    = {10x-8}/{(x-2)(x+2)} + {-(9x-2-x^2)}/{(x-2)(x+2)}
    = {10x-8-(9x-2-x^2)}/{(x-2)(x+2)}
    = {10x-8-9x+2+x^2}/{(x-2)(x+2)}
    = {x-6+x^2}/{(x-2)(x+2)}
    = {(x-2)(x+3)}/{(x-2)(x+2)}
    = {x+3}/{x+2}  

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

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