3) 2√2 xy-x²-2y²
=-[x²-2*x*√2 y+(√2 y)²]
=-[x-√2 y]²
4) 3√3 xy-9x²-3/4 y²
=-[(3x)²-2*3x*√3 /2 y+(√3 /2 y)²
=-[3x-√3 /2 y]²
5) 3x²+3/4 y² -3xy
= [(√3 x)²-2*√3 x*√3 /2 y+(√3/ 2 y)² ]
= [√3 x-√3/ 2 y]²
6) 3x²-3/4 y²
= (√3 x)²-(√3/ 2 y)²
= (√3 x - √3/ 2 y)(√3 x + √3/ 2 y)
7) -5x²+6y²
= (√6 y)²-(√5 x)²
= (√6 y-√5 x)(√6 y+√5 x)
8) 1/8 x³+6xy² + 3/2 x²y + 8y³
= (1/2 x)³ +3 * (1/2 x)² *2y + 3* 1/2 x *(2y)²+(2y)³
= (1/2 x + 2y)³
9) 1/8 x³+1/6 xy² + 1/4 x²y + 1/27 y³
= (1/2 x)³+ 3*(1/2 x)²*(1/3 y)+3*(1/2 x)*(1/3 y)²+(1/3 y)³
= (1/2 x +1/3 y)³
10) -x³-27xy²-9x²y-27y³
= -[x³+3*x²*3y+3*x*(3y)²+(3y)³]
= -[x+3y]³
11) x³+1/3 xy² - 1/9 x²y - 1/27 y³
= x³ -3*x²*(1/3 y)+3*x*(1/3 y)² - (1/3 y)³
= (x - 1/3 y)³
12) 8x³+2/3 xy² - 4x²y - 1/27 y³
= (2x)³-3*(2x)²*(1/3 y)+3*(2x)*(1/3 y)²-(1/3 y)³
= (2x- 1/3 y)³
