\(A\left(x\right)=43x-\left(52x^2+34x^2-8x^4\right)-\left(8x^4+16x^3-42x^2+43x\right)+19\)

\(\Leftrightarrow A\left(x\right)=43x-86x^2+8x^4-16x^3+42x^2-43x+19\)

\(\Leftrightarrow A\left(x\right)=-16x^3-44x^2+19\)

Bậc là: 3

Với x ≥ 0 thì √3x có nghĩa. Ta có:

Qui đồng rồi khử mẫu, ta được:

\(4x+12.\left(27-x\right)=15x+5.\left(27-x\right)\)

\(\Leftrightarrow4x+324-12x=15x+135-5x\)

\(\Leftrightarrow4x-12x-15x+5x=135-324\)

\(\Leftrightarrow-18x=-189\Leftrightarrow x=\frac{21}{2}=10,5\)

Vậy x = 10,5

\(\frac{x}{15}+\frac{27-x}{5}=\frac{x}{4}+\frac{27-x}{12}\)

\(\frac{x}{15}+\frac{3\left(27-x\right)}{15}=\frac{3x}{12}+\frac{27-x}{12}\)

\(\frac{x}{15}+\frac{81-3x}{15}=\frac{3x}{12}+\frac{27-x}{12}\)

\(\frac{x+81-3x}{15}=\frac{3x+27-x}{12}\)

\(\frac{-2x+81}{15}=\frac{2x+27}{12}\)

\(12\left(-2x+81\right)=15\left(2x+27\right)\)

\(-24x+972=30x+405\)

\(972-405=30x+24x\)

\(567=54x\)

\(x=567:54\)

\(x=10,5\)

\(\frac{x}{15}+\frac{27-x}{5}=\frac{x}{4}+\frac{27-x}{12}\)

\(\Leftrightarrow\frac{4x}{60}+\frac{12\left(27-x\right)}{5}=\frac{15x}{60}+\frac{5\left(27-x\right)}{12}\)

\(\Leftrightarrow4x+324-12x=15x+135-5x\)

\(\Leftrightarrow4x-12x-15x+5x=135-324\)

\(\Leftrightarrow-18x=-189\)

\(x=\frac{-189}{-18}=\frac{21}{2}=10,5\)

a) Với x ≥ 0 thì √3x có nghĩa. Ta có:

b) Với x ≥ 0 thì √2x có nghĩa. Ta có

\(\text{a, 3(x+1)+4x=10}\)

\(\Rightarrow3x+3+4x=10\)

\(\Rightarrow7x+3=10\)

\(\Rightarrow7x=10-3=7\)

\(\Rightarrow x=1\)

c, x+1/10+x+2/9=x+3/8+x+4/7

=> (x+1/10 +1) +(x+2/9 +1)= ( x+3/8 +1) +(x+4/7 +1)

=> x+11/10 + x+11/9 = x+11/8 + x+11/7

...............

a) \(3\left(x+1\right)+4x=10\)

\(\Rightarrow3x+3+4x=10\)

\(\Rightarrow3x+4x=10-3\)

\(\Rightarrow7x=7\)

\(\Rightarrow x=7\)

Đáp án là D