Đáp án + Giải thích các bước giải:
CT: `(A±B)^2=A^2±2AB+B^2`
`A^2-B^2=(A-B)(A+B)`
Bài 4:
`a)37^2+2.37.63+63^2=(37+63)^2=100^2=10000`
`b)42^2+84.58+58^2= 42^2+2.42.58+58^2`
`=(42+58)^2=100^2=10000`
`c)121^2-2.121.21+21^2=(121-21)^2=100^2=10000`
`d)65^2-130.15+15^2=65^2-2.65.15+15^2`
`=(65-15)^2=50^2=2500`
Bài 5:
`a)x^2+2x+1=(x+1)^2`
`b)x^2+4x+4=x^2+2.x.2+2^2=(x+2)^2`
`c)x^2+6x+9=x^2+2.x.3+3^2=(x+3)^2`
`d)x^2-x+1/4=x^2+2.x.1/2+(1/2)^2=(x+1/2)^2`
`e)x^2-8x+16=x^2-2.x.4+4^2=(x-4)^2`
`f)9x^2+6x+1=(3x)^2+2.3x.1+1^2=(3x+1)^2`
Bài 6:
`a)x^2+10x+26+y^2+2y=(x^2+2.x.5+5^2)+(y^2+2y+1)`
`=(x+5)^2+(y+1)^2`
`b)x^2-2xy+2y^2+2y+1=(x^2-2xy+y^2)+(y^2+2y+1)`
`=(x-y)^2+(y+1)^2`
`c)4x^2-12x-y^2+2y+8=(2x)^2-2.2x.3+3^2-(y^2-2y+1)`
`=(2x-3)^2-(y-1)^2=(2x-3-y+1)(2x-3+y-1)`
`=(2x-y-2)(2x+y-4)`
Bài 7:
`a)(x+y+4)(x+y-4)=(x+y)^2-4^2=(x+y)^2-16`
`b)(y+2z-3)(y-2z+3)=y^2-(2z-3)^2`
Mk xin hay nhất ạ
