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chi tiết

\(F=\dfrac{5}{6}\cdot\dfrac{11}{3}-\dfrac{5}{3}\cdot\dfrac{8}{6}=\dfrac{55}{18}-\dfrac{20}{9}=\dfrac{55}{18}-\dfrac{40}{18}\)

\(=\dfrac{15}{18}=\dfrac{5}{6}.\)

\(Bài1\)

\(a.A=7x-5-x^2+8x-1+x^2\)\(A=7x+8x-5-1-x^2+x^2\)

\(A=15x-6.\)

\(b.B=x-4+3x^2+x-4x^2-1\)

\(B=x+x+3x^2-4x^2-4-1\)

\(B=-x^2+2x-5.\)

\(c.C=\left(2x-9+x^2\right)-\left(5-x+x^2\right)\)

\(C=2x-9+x^2-5+x-x^2\)

\(C=2x+x-9-5+x^2-x^2\)

\(C=3x-14.\)

\(d.D=5x-\left(1-3x\right)+\left(x^2-x+7\right)\)

\(D=5x-1+3x+x^2-x+7\)

\(D=5x+3x-x+x^2-1+7\)

\(D=x^2+7x+6.\)

\(Bài2\)

\(a.A=x^2-2\cdot x+\left(-x\right)+5\) \(tại\) \(x=2\)

\(A=x^2-2x-x+5\)

\(A=x^2-3x+5\) \(tại\) \(x=2.\)

\(A=2^2-3\cdot2+5\cdot2=4\cdot6+10=240.\)

\(b.B=x^2-x+5\) \(tại\) \(x=-4\)

\(B=-4x^2-4+5\cdot\left(-4\right)\)

\(B=-16-4+\left(-20\right)\)

\(B=\left(-20\right)+\left(-20\right)=-40\)

\(Bài 3. Ko biết .\)

\(Bài 5.\)

\(a.x\cdot5x=5x^2.\)                   \(b.4x\cdot x^2=4x^3.\)

\(c.2\cdot x\left(-3x^0\cdot x^2\right)=-2x\cdot\left(3x^0\cdot x^2\right)=-6x\cdot x^2\cdot x=-6x^3.\)

\(d.3\cdot x\left(-x\right)=-3x\cdot x=-3x^2.\)

\(e.\left(5x\right)^2\cdot\left(-x\right)=-\left(5x\right)^2\cdot x=-x\cdot\left(5x\right)^2\)\(=-x\cdot25x^2=25x^3.\)

\(bài 6. Ko biết\)

\(Bài7\)

\(a.A=5x^2y\left(x-7\right)-5xy\left(7-x\right)\)

\(A=5x^3y-35x^2y-35xy+5x^2y\)

\(A=5x^3y-35x^2y+5x^2y-35xy\)

\(A=5x^3y-30x^2y-35xy.\)

\(b.B=ab\left(x-2\right)-a^2\left(x-2\right)\)

\(B=abx-2ab-xa^2+2a^2.\)

\(c.C=4x^3y^2-8x^2y^3+12x^3y\)

\(C=4x^2y\cdot xy-4x^2y\cdot2y^2+4x^2y\cdot3x\)

\(C=4x^2y\left(xy-2y^2+3x\right).\)

\(\dfrac{\sqrt{5}-\sqrt{2}}{\sqrt{5}+\sqrt{2}}-\dfrac{\sqrt{5}+\sqrt{2}}{\sqrt{5}-\sqrt{2}}-\dfrac{2}{\sqrt{10}}\)

\(=\dfrac{7-2\sqrt{10}}{3}-\dfrac{\sqrt{5}+\sqrt{2}}{\sqrt{5}-\sqrt{2}}-\dfrac{2}{\sqrt{10}}\)\(=\dfrac{7-2\sqrt{10}}{3}-\dfrac{7+2\sqrt{10}}{3}-\dfrac{2}{\sqrt{10}}\)

\(=\dfrac{7-2\sqrt{10}}{3}-\dfrac{7+2\sqrt{10}}{3}-\dfrac{\sqrt{2}}{\sqrt{5}}=-\dfrac{4\sqrt{10}}{3}-\dfrac{\sqrt{2}}{\sqrt{5}}.\)

\(\dfrac{2x^2}{3y^2}\cdot\dfrac{y^2}{x-2ax}+\dfrac{3x}{3a}=\dfrac{2x}{3\left(1-2a\right)}+\dfrac{3x}{3a}=\dfrac{2x}{3\left(1-2a\right)}+\dfrac{x}{a}.\)

\(a.x\cdot5x=5x^2.\)

\(b.4x\cdot x^2=4x^3.\)

\(c.2\cdot x\left(-3x^0\cdot x^2\right)\)\(=-6x^3.\)

\(d.3\cdot x\left(-x\right)=3x\cdot\left(-x\right)=-3x^2.\)

\(e.\left(5x\right)^2\cdot\left(-x\right)=-25x^3.\)

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