1.(2x+5y)²=4x²+20x+25y²
2. (9d-8k)(9d+8k)=81d²-64k²
3. (x+7y)²-14xy==x²+14xy+49y²-14xy=x²+49y²
<span>4. (m-3n)(m+3n)+(3n-4)²=m²-9n²+9n²-24n+16=m²-24n+16
5. s^4+7s^2+N=(s²)²+2·s²·3,5+(3,5)²
N=3,5²=12,25
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X1+x2=-b
3+5=-b
b=-8
x1*x2=3*5=15
x²-8x+15=0