Bài 2:
a: \(\left(x-9\right)^2-x\left(x-9\right)-2=10\)
=>\(x^2-18x+81-x^2+9x-2=10\)
=>-9x+79=10
=>-9x=10-79=-69
=>x=69/9=23/3
b: \(49x^2-14\sqrt5x+6=5\)
=>\(\left(7x\right)^2-2\cdot7x\cdot\sqrt5+5+1=5\)
=>\(\left(7x-\sqrt5\right)^2=4\)
=>\(\left[\begin{array}{l}7x-\sqrt5=2\\ 7x-\sqrt5=-2\end{array}\right.\Rightarrow\left[\begin{array}{l}7x=2+\sqrt5\\ 7x=\sqrt5-2\end{array}\right.\Rightarrow\left[\begin{array}{l}x=\frac{2+\sqrt5}{7}\\ x=\frac{\sqrt5-2}{7}\end{array}\right.\)
Bài 1:
a: \(4x^2\left(x-y\right)+5y-5x\)
\(=4x^2\left(x-y\right)-5\left(x-y\right)\)
\(=\left(x-y\right)\left(4x^2-5\right)\)
b: \(5x^2-x+y-5y^2\)
\(=5\left(x^2-y^2\right)-\left(x-y\right)\)
=5(x-y)(x+y)-(x-y)
=(x-y)(5x+5y-1)
c: \(25a^2+10a-9b^2+1\)
\(=\left(25a^2+10a+1\right)-9b^2\)
\(=\left(5a+1\right)^2-\left(3b\right)^2\)
=(5a+1-3b)(5a+1+3b)
d: \(x^3-64y^3+3x^2+3x+1\)
\(=\left(x^3+3x^2+3x+1\right)-64y^3\)
\(=\left(x+1\right)^3-\left(4y\right)^3\)
=(x+1-4y)\(\left\lbrack\left(x+1\right)^2+4y\left(x+1\right)+16y^2\right\rbrack\)
