Вот подробное решение. Смотрите, разбирайте :)
(2m-3n)(5m+n)-10(m+n)² = 10m²+2mn-15mn-3n² -10(m²+2mn+n²) =
= 10m²+2mn-15mn-3n²-10m²-20mn-10n² = -33mn-13n² = -n(33m-13n)
<span>1) (m-1)^2-121=</span>m^2-2m+1-121=m^2-2m-120=(x-12)(x+10)
<span>2) x^2-144=0</span>
D=0^2-4*1*(-144)=576
x1=24/2=12
x2=-24/2=-12
<span>3) 125+n^3<span>=5^3+n^3=(5+n)(25-5n+n^2) </span>
4) (87^3-42^3)/15=</span>(658503-74088)/15=584415/15=38961
(x+4)²=3y⇒12y=4(x+4)²
(4x+1)²=12y⇒(4x+1)²=4(x+4)²
16x²+8x+1-4x²-32x-64=0
12x²-24x-63=0
4x²-8x-21=0
D=64+336=400
x1=(8-20)/8=-1,5
x2=(8+20)/8=3,5
3y=(-1,5+4)²=2.5²=6,25⇒y1=25/12
3y=(3,5+4)²=7,5²=56,25⇒y2=225/12