<span>( х -67.2) +4.2 =17.4-20.1
х-67,2+4,2=-2,7
х-63=-2,7
х=-2,7+63
х=60,3
</span><span>-100.9-(47.27-х)=5.82-90
-100,9-47,27+х=-84,18
-148,17+х=-84,18
х=-84,18+148,17
х=63,99</span>
8*2=16 (1)
8:2=4 (2)
8-2=6 (3)
53 2/3 : 7/9 = 161/3 : 7/9 = 161/3 * 9/7 = 69 км/ч - скорость автомобиля.
В)(х¹⁰-у⁵)(х¹⁰+у⁵)=(х¹⁰)²-(у⁵)²=х²⁰-у¹⁰
г)(2m+n)²=(2m)²+2*2mn+n²=4m²+4mn+n²
д) (4а-5)²=(4а)²-2*4а*5+5²=16а²-40а+25
е) (х+у)(х²-ху+у²)=х³-у³
3.
а) 92²=(100-8)²=100²-2*100*8+8²=10000-1600+64=8464
б) 68²-58²=(68-58)(68+58)=10*126=1260
4.
а) 16x⁷y⁵z³-72y⁶z²=8y⁵z²(2x⁷z-9y)
б) -18х²+12х-3ху+2у=-6х(3х-2)-у(3х-2)=(-6х-у)(3х-2)=-(6х-у)(3х-2)
в) 40х²+200х+250=10(4х²+20х+25)=10((2х)²+2*2х*5+5²)=10(2х+5)²
г) 10(81х²-100у²)=10((9х)²-(10у)²)=10(9х-10у)(9х+10у)
(x-380)*50=200
50x-19000=2000
50x=21000
x=420
or
(x-380)*50=200
50x-19000=2000
50x=21000
вот и два действия )
ок
(x+8)/70=4
x+8=280
x=280-8
x=272