Объяснение:

7.

[tex]a)\ (3p+2a)(3p-2a)=9p^2-4a^2.\\b)\ (3p^2+4p)(4p-3p^2)=16p^2-9p^4.\\c)\ (0,3p+0,1b)(0,3p-0,1b)=0,09p^2-0,01b^2.\\d)\ (0,04p^2+3a^2)(3a^2-0,04p^2)=9a^4-0,0016p^4.[/tex]

8.

[tex]a)\ 4a^2-25b^2=(2a)^2-(5b)^2=(2a+5b)(2a-5b).\\b)\ 4a^2x^2-25b^2=(2ax)^2-(5b)^2=(2ax+5b)(2ax-5b).\\c)\ 0,0001-\frac{1}{25}a^2=0,01^2-(\frac{a}{5})^2=(0,01+\frac{a}{5})*(0,01-\frac{a}{5}).\\ d)\ 0,04a^2-\frac{49}{9} b^2=(0,2a)^2-(\frac{7}{3} b)^2=(0,2a+\frac{7}{3}b)(0,2a-\frac{7}{3}b).[/tex]

9.

[tex]3x+5y=9\ \ \ \ \ \\9x^2-25y^2=45\\\ (3x)^2-(5y)^2=45\\(3x+5y)(3x-5y)=45\\9*(3x-5y)=45\ |:9\\3x-5y=5.[/tex]

10.

[tex]5y-2x=7\\25y^2-4x^2=35\\(5y)^2-(2x)^2=35\\(5y-2x)(5y+2x)=35\\7*(5y+2x)=35\ |:7\\5y+2x=2x+5y=5.[/tex]