4
1) х²+10х+25-16 = х²+10х+9 = х²+х+9х+9 = х(х+1)+9(х+1)=(х+1)(х+9)
2) 81-m²+14m-49 = -m²+14m+32 = -m²+16m-2m+32 = -m(m-16)-2(m-16) =
= (m-16)(-m-2)
5
1) a² - a - b² - b = (a²-b²)-(a+b) = (a-b)(a+b)-(a+b) = (a+b)(a-b-1)
2) y² + yx -xz - z² = (y²-z²)+(yx-xz) = (y-z)(y+z)+x(y-z) = (y-z)(y+z+x)
2с(a+1)+b(a+1)=(a+1)(2c+b)
-4=15х+13
-15х=4+13
-15х=17
х=17+15
х=32
S=a*b/2
a*b=2S
a=b+7
(b+7)*b=2*15
b^2+7b=30
b^2+7b-30=0
D=49+120=169
√D=13
b1=(-7+13)/2=3
b2=(-7-13)/2= - 10 - не подходит по смыслу, т.к. b>0
Значит b= 3 см, а=3+7 = 10 см