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a) \(\left(1+x\right)^2+\left(1-x\right)^2\)
\(=1+2x+x^2+1-2x+x^2\)
\(=2x^2+2\)
b) \(\left(x+2\right)^2+\left(1+x\right)\left(1-x\right)\)
\(=x^2+4x+4+1-x^2\)
\(=4x+5\)
c) \(\left(x-3\right)^2+3\left(x+1\right)^2\)
\(=x^2-6x+9+3x^2+6x+3\)
\(=4x^2+12\)
d)\(\left(2+3x\right)\left(3x-2\right)-\left(3x+1\right)^2\)
\(=9x^2-4-9x^2-6x-1\)
\(=-6x-5\)
e) \(\left(x+5\right)\left(x-2\right)-\left(x+2\right)^2\)
\(=x^2-2x+5x-10-x^2-4x-4\)
\(=-x-14\)
f) \(\left(x+3\right)\left(2x-5\right)-2\left(1+x\right)^2\)
\(=2x^2-5x+6x-15-2-4x-2x^2\)
\(=-3x-17\)
g) \(\left(4x-1\right)\left(4x+1\right)-4\left(1-2x\right)^2\)
\(=16x^2-1-4+16x-16x^2\)
\(=16x-5\)
#Học tốt!
a, \(\left(x+4\right)^2-\left(x+1\right)\left(x-1\right)=16\)
\(\Leftrightarrow x^2+8x+16-\left(x^2-x+x-1\right)=16\)
\(\Leftrightarrow8x+1=0\Leftrightarrow x=-\frac{1}{8}\)
b, \(\left(2x-1\right)^2+\left(x+3\right)^2-5\left(x+7\right)\left(x-7\right)=0\)
\(\Leftrightarrow4x^2-4x+1+x^2+6x+9-5\left(x^2-49\right)=0\)
\(\Leftrightarrow2x+255=0\Leftrightarrow x=-\frac{225}{2}\)
c, \(\left(x+2\right)\left(x-2\right)-x^3-2x=15\)
\(\Leftrightarrow x^2-4-x^3-2x=15\)( vô nghiệm )
d, \(\left(x+3\right)^3-x\left(3x+1\right)^2+\left(2x+1\right)\left(4x^2-2x+1\right)=28\)
\(\Leftrightarrow x^3+9x^2+27x+27-9x^3+6x^2-x+8x^3+1=28\)
\(\Leftrightarrow15x^2+26=0\Leftrightarrow x^2\ne-\frac{26}{15}\)( vô nghiệm )
Tính nhẩm hết á, sai bỏ quá nhá, sắp đi hc ... nên chất lượng hơi kém xíu ~~~
a)
\((x^2+x)^2+3(x^2+x)+2\)
\(=(x^2+x)^2+(x^2+x)+2(x^2+x)+2\)
\(=(x^2+x)(x^2+x+1)+2(x^2+x+1)\)
\(=(x^2+x+2)(x^2+x+1)\)
b) \(x(x+1)(x+2)(x+3)+1\)
\(=[x(x+3)][(x+1)(x+2)]+1\)
\(=(x^2+3x)(x^2+3x+2)+1\)
\(=(x^2+3x)^2+2(x^2+3x)+1\)
\(=(x^2+3x+1)^2\)
c) \((x^2+x+1)(x^2+3x+1)+x^2\)
\(=(x^2+x+1)[(x^2+x+1)+2x]+x^2\)
\(=(x^2+x+1)^2+2x(x^2+x+1)+x^2\)
\(=(x^2+x+1+x)^2\)
\(=(x^2+2x+1)^2=[(x+1)^2]^2=(x+1)^4\)
d) \((x^2+1)^2-4x(1-x^2)\)
\(=(x^2+1)^2+4x(x^2-1)\)
\(=(x^2+1)^2+(x-1)(4x^2+4x)\)
\(=(x^2+1)^2+(x-1)[4x^2+4+(4x-4)]\)
\(=(x^2+1)^2+(4x^2+4)(x-1)+(4x-4)(x-1)\)
\(=(x^2+1)^2+2(x^2+1)(2x-2)+(2x-2)^2\)
\(=(x^2+1+2x-2)^2=(x^2+2x-1)^2\)
\(Q\left(x\right).\left(x-2\right)+28=\left(x^2+x+1\right)\left(x+2\right)\)
\(\Rightarrow Q\left(x\right).\left(x-2\right)+28=x^3+2x^2+x^2+2x+x+2\)
\(\Rightarrow Q\left(x\right).\left(x-2\right)=x^3+3x^2+3x-26\)
\(\Rightarrow Q\left(x\right)=\frac{x^3-2x^2+5x^2-10x+13x-26}{x-2}\)
\(=\frac{x^2.\left(x-2\right)+5x.\left(x-2\right)+13.\left(x-2\right)}{x-2}\)
\(=\frac{\left(x-2\right).\left(x^2+5x+13\right)}{x-2}\)
\(=x^2+5x+13\)