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\(\left(2a+b\right)^2-\left(2a+a\right)^2\)
\(=\left(2a+b-2a-a\right)\left(2a+b+2a+a\right)\)
\(=\left(b-a\right)\left(5a+b\right)\)
\(\left(2a+b\right)^2-\left(2a+a\right)^2\)
\(=\left(2a+b\right)^2-\left(3a\right)^2\)
\(=\left(2a+b-3a\right)\left(2a+b+3a\right)\)
\(=\left(b-a\right)\left(5a+b\right)\)
1.
a)\(\frac{4}{9}x^2+\frac{4}{3}xy+y^2\)
b)\(9a^2+3ab+\frac{1}{4}a^2\)
2.
a)\(\left(5x+2b\right)^2\)
b)\(\left(x+1\right)^2\)
c)\(\left(3x+1\right)^2\)
d)\(\left[\left(2x+3y\right)+1\right]^2\)
a) \(2a^{n+2}b^n-18a^nb^{n+2}\)
\(=2a^nb^n\left(a^2-9b^2\right)\)
\(=2a^nb^n\left(a-3b\right)\left(a+3b\right)\)
\(x^2+y^2-xy-2x-2y+9=x^2+y^2+2xy-2x-2y+9-3xy\)
\(=\left(x+y\right)^2-2\left(x+y\right)+9-3xy=\left(x+y-2\right)\left(x+y\right)+9-3xy.\)
\(đếnđâytịt\)
b
c, =3 dễ
\(\frac{3x^2-6x+9}{x^2-2x+3}=\frac{3\left(x^2-2x+3\right)}{x^2-2x+3}=3\)
\(x^4+6x^3+7x^2-6x+1=x^4-2x^2+1+6x^3-6x+9x^2=\left(x^2-1\right)^2+6x\left(x^2-1\right)+9x^2=\left(x^2-1\right)^2+2.3x\left(x^2-1\right)+\left(3x\right)^2=\)
\(\left(x^2+3x-1\right)^2\)
\(x^4+6x^3+7x^2-6x+1=\left(x^2+ax+1\right)\left(x^2+bx+1\right)hoặc=\left(x^2+cx-1\right)\left(x^2+dx-1\right)\)
+\(x^4+6x^3+7x^2-6x+1=\left(x^2+ax+1\right)\left(x^2+bx+1\right)=x^4+\left(a+b\right)x^3+\left(ab+2\right)x^2+\left(a+b\right)x+1\)=> a+b=6 ; ab+2 =7 ; a+b =-6 loại
+\(x^4+6x^3+7x^2-6x+1=\left(x^2+cx-1\right)\left(x^2+dx-1\right)=x^4+\left(c+d\right)x^3+\left(cd-2\right)x^2-\left(c+d\right)x+1\)=>c+d =6 ; cd-2 =7 ; hay c+d =6 ; cd =9 => c =d =3
vậy \(x^4+6x^3+7x^2-6x+1=\left(x^2+3x-1\right)\left(x^2+3x-1\right)\)
Bạn tphaan tích tiếp nhé ( Bấm máy tính giải pt )
\(\dfrac{1}{9}-\dfrac{2}{3}y^4+y^8=\left(\dfrac{1}{3}\right)^2-2.\dfrac{1}{3}.y^4+\left(y^4\right)^2=\left(\dfrac{1}{3}+y^4\right)^2\)
Cho mình sửa lại thành: \(\left(\dfrac{1}{3}-y^4\right)^2\)