`#Sad`
`25)`
`a,`
`A= x^3+15x^2+75x+125`
`A= x^3+3. 5. x^2+3. 5^2. x+5^3`
`A= (x+5)^3`
`\text{→Thay}` `x=-10` `\text{vào ta có:}`
`A= (-10+5)^3`
`A= 5^3`
`A= 125`
`b,`
`B= x^3-9x^2+27x-27`
`B= x^3-3. x^2. 3+3. x. 3^2-3^3`
`B= (x-3)^3`
`\text{→Thay}` `x=13` `\text{vào ta có:}`
`B= (13-3)^3`
`B= 10^3`
`B= 1000`
`c,`
`C= (x^3)/(8)+(x^2y)/(4)+(xy^2)/(6)+(y^3)/(27)`
`C= (x/2)^3+3. (x/2)^2. y/3+3. x/2. (y/3)^2+(y/3)^3`
`C= (x/2+y/3)^3`
`\text{→Thay}` `=-8` `\text{và}` `y=6` `\text{vào ta có:}`
`C= [(-8/2)+6/3]^3`
`C= (-2)^3`
`C= -8`
