<span>sin^2 α=1-cos^2α; 5 sin^2 α=5-5cos^2α; 5 sin^2 α-cos^2α=5-6cos^2α=5-6*0,25=5-1,5=3,5</span>
<span>1)2.5(4 - 2x) - 5(1 - 3x) = 5
10-5x-5+15x=5
10x=0
x=0
2) 2/3(3x - 1) - 1/9 (9х - 2 1/4) = 1/4
2x-2/3-x+1/9 *9/4=1/4
x=1/4+2/3-1/4
x=2/3
3) -2.4 /2.3 = х / 6.9
x=-2.4*6.9/2.3
y=-7.2
4) у / (-3.5) = 4 /1.4
y=-3.5*4/1.4
y=-10
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198698+(150036-74946):30*400
1) 150036-74946=75090
2) 75090:30=2503
3) 2503*400 = 1001200
4) 1001200+198698=1199898
(92578+3206)*800-(50010-3215)*90
1)92578+3206=95783
2)50010-3215=46795
3)95783*800=76626400
4)46795*90=4227750
5) 76626400-4227750=72398650
(42071-970*40)*7000-48000:80+256740*600
1) 970*40=38800
2)42071-38800=3271
3)3271*7000=22897000
4)48000:80=600
5)256740*600=154044000
6)22897000-600=22896400
7)22896400+154044000=176940400
5 м кв - 50 л
7 м кв - х
5х=7*50
5х=350
х=350:5
х=70 литров воды потребуется
<span>2а(а+b-c)-2b(a-b-c)+2c(a-b+c)=2a^2+2ab-2ac-2ab+2b^2+2bc+2ac-2bc+2c^2=2a^2+2b^2+2c^2=2(a^+b^2+c^2)</span>