B, ( x + y )^3 + ( x – y )^3 C, x – 6x + 9 D, ( x^2 – 25 ) ^2 9 – ( x – 5 ) ^2 29/08/2021 Bởi Genesis B, ( x + y )^3 + ( x – y )^3 C, x – 6x + 9 D, ( x^2 – 25 ) ^2 9 – ( x – 5 ) ^2
Đáp án: x^3+3x^2y+3xy^2+y^3-x^3+3x^2y-3xy^2+y^3=6x^2y x^2-6x+9= (x-3)^2 ((x^2-25)*3)^2-(x-5)^2=((x^2-25)*3-x+5)((x^2-25)*3+x-5)=((x-5)(x+5)*3-(x-5))((x-5)(x+5)*3+(x-5)=(x-5)^2(3x+14)(3x+16) Bình luận
B, ( x + y )^3 + ( x – y )^3= [( x+y) + (x-y)][ (x+y)² – (x+y)(x-y) + (x-y)²] = 2x( x² + 2xy+ y² – x² + y²+ x²- 2xy + y²) = 2x( x² + 3y²) C, x – 6x + 9= (x+3)² D, ( x^2 – 25 ) ^2 – ( x – 5 ) ^2= ( x² -25 – x+ 5)( x² -25+ x-5) = (x² -20- x)( x²- 30+x) ² Bình luận
Đáp án:
x^3+3x^2y+3xy^2+y^3-x^3+3x^2y-3xy^2+y^3=6x^2y
x^2-6x+9= (x-3)^2
((x^2-25)*3)^2-(x-5)^2=((x^2-25)*3-x+5)((x^2-25)*3+x-5)=((x-5)(x+5)*3-(x-5))((x-5)(x+5)*3+(x-5)=(x-5)^2(3x+14)(3x+16)
B, ( x + y )^3 + ( x – y )^3= [( x+y) + (x-y)][ (x+y)² – (x+y)(x-y) + (x-y)²]
= 2x( x² + 2xy+ y² – x² + y²+ x²- 2xy + y²)
= 2x( x² + 3y²)
C, x – 6x + 9= (x+3)²
D, ( x^2 – 25 ) ^2 – ( x – 5 ) ^2= ( x² -25 – x+ 5)( x² -25+ x-5)
= (x² -20- x)( x²- 30+x)
²