= ab^2 - ac^2 + bc^2 - a^2b + a^2c -cb^2

=ab(b-a) - ac(c-a) - bc(b-c)

=ab(b-a) - ac(c-a) - bc(b-c)

=ab(b-a) - ac(-a+b-b+c) - bc(b-c)

=ab(b-a) - ac(b-a) + ac(b-c) - bc(b-c)

=(b-a)(ab-ac) - (b-c)(ac-bc)

=a(b-c)(b-a) - ac(a-b)(b-c)

=(b-c)[a(b-a) - c(b-a)]

=(b-c)(b-a)(a-c)

a, \(\frac{3x}{2x+4};\frac{x+3}{x^2-4}\)

Ta có : \(2x+4=2\left(x+2\right)\)

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

MTC : \(2\left(x-2\right)\left(x+2\right)\)

\(\frac{3x}{2x+4}=\frac{3x}{2\left(x+2\right)}=\frac{3x\left(x-2\right)}{2\left(x-2\right)\left(x+2\right)}=\frac{3x^2-6x}{2\left(x-2\right)\left(x+2\right)}\)

\(\frac{x+3}{x^2-4}=\frac{x+3}{\left(x-2\right)\left(x+2\right)}=\frac{2x+6}{\left(x-2\right)\left(x+2\right)}\)

c, \(\frac{2x}{x^2-8x+16};\frac{x}{3x^2-12x}\)

Ta có : \(x^2-8x+16=\left(x-4\right)^2\)

\(3x^2-12x=3x\left(x-4\right)\)

MTC : \(3x\left(x-4\right)^2\)

\(\frac{2x}{x^2-8x+16}=\frac{2x}{\left(x-4\right)^2}=\frac{6x^2}{3x\left(x-4\right)^2}\)

\(\frac{x}{3x^2-12x}=\frac{x}{3x\left(x-4\right)}=\frac{x^2+4x}{3x\left(x-4\right)\left(x+4\right)}\)

x²+y²=(x+y)²-2xy
        =9²-2.14

        =53

mink làm ùi đó bạn tick cho mink nha

4x²-5=4

4x²    =4+5=9

x²     =9:4

x²    =2,25

x     =1,5