so do la 117

tick nha

a) \(x^4+4\)

\(=x^4+4x^2+4-4x^2\)

\(=\left(x^2+2\right)^2-\left(2x\right)^2\)

\(=\left(x^2+2-2x\right)\left(x^2+2+2x\right)\)

b) \(4x^4+81\)

\(=4x^4+81+36x^2-36x^2\)

\(=\left(2x^2+9\right)^2-\left(6x\right)^2\)

\(=\left(2x^2+9-6x\right)\left(2x^2+9+6x\right)\)

c) \(x^4+64y^4\)

\(=x^4+64y^4+16x^2y^2-16x^2y^2\)

\(=\left(8y^2+x^2\right)^2-\left(4xy\right)^2\)

\(=\left(8y^2+x^2-4xy\right)\left(8y^2+x^2+4xy\right)\)

d) \(x^4y^4+4\)

\(=x^4y^4+4+4xy^2-4xy^2\)

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

\(=\left(x^2y^2+2-2xy\right)\left(x^2y^2+2+2xy\right)\)

\(\left[\left(8x-14\right):4\right].27=36\)

\(\Leftrightarrow\left[\left(8x-14\right):4\right]=36:27\)

\(\Leftrightarrow\left[\left(8x-14\right):4\right]=\dfrac{4}{3}\)

\(\Leftrightarrow8x-14=\dfrac{4}{3}.4\)

\(\Leftrightarrow8x-14=\dfrac{16}{3}\)

\(\Leftrightarrow8x=\dfrac{16}{3}+14\)

\(\Leftrightarrow8x=\dfrac{58}{3}\)

\(\Leftrightarrow x=\dfrac{29}{12}\)

\(7.\left(5x+2y\right)-2.\left(9x+7y\right)\)

\(=35x+14y-18x-14y\)

\(=35x-18x\)

\(=17x\)