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Đáp án:
a, (2x+3y)^2=2x^2+2*2x*3y+3y^3
b,(5x-y)^2
=5x^2-2*5x-y+y^2
c,(x+1/4)^2
=x^2+2x+(1/4)^2
=x^2+1/2x+1/16
e,(3x+1)(3x-1)
=9x^2-3x+3x-1
=9x^2-1
mk chi bt lm nhiu thôi
Giải thích các bước giải:
1 2
a(2x+3y)^2=4x^2+12xy+9y^2 a x^2-6x+9=(x+3)^2
b(5x-y)^2=25x^2-10xy+y^2 b1/4a^2+2ab^2+b^4=(1/2a+b^2)^2
c(x+1/4)^2=x^2+1/8x+1/16 c 25+10x+x^2=(5+x0^2
d(1/3x-1/2y)^2=1/9x^2-1/3xy+1/4y^2 d 1/9-2/3y^4+y^8=(1/3-y^4)^2
e(3x+1)(3x-1)=9x^2-1 e (x+4)(x^2-4+16)=x^2+16
f(x^2+2/5y)(x^2-2/5y)=x^4-4/25y^2 f (1/3x+2y)(1/9x^2-2/3xy+4y^2)=1/9x^2+4y^2
g(2x+y^2)^3=8x^3+6x^2y^2+6x^4+y^6 g (x-3y)(x^2-3xy+9y^2)=x^2-9y^2
h(1/2x^2+1/3y)^3=1/8x^6+1/2x^4y+1/2x^2y^2+1/9y^3
h (x^2-1/3)(x^4+1/3x^2+1/9)=x^4-1/9