1. 390 : (4х + 3) = 26 2. 528 : (5х - 7) = 16
4х + 3 = 390 : 26 5х - 7 = 528 : 16
4х + 3 = 15 5х - 7 = 33
4х = 15 - 3 5х = 33 + 7
4х = 12 5х = 40
х = 12 : 4 х = 40 : 5
х = 3 х = 8
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3. 594 : (8х - 55) = 18 4. 735 : (6х + 17) = 21
8х - 55 = 594 : 18 6х + 17 = 735 : 21
8х - 55 = 33 6х + 17 = 35
8х = 33 + 55 6х = 35 - 17
8х = 88 6х = 18
х = 88 : 8 х = 18 : 6
х = 11 х = 3
1. 390 : (4х + 3) = 26 2. 528 : (5х - 7) = 16
4х + 3 = 390 : 26 5х - 7 = 528 : 16
4х + 3 = 15 5х - 7 = 33
4х = 15 - 3 5х = 33 + 7
4х = 12 5х = 40
х = 12 : 4 х = 40 : 5
х = 3 х = 8
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3. 594 : (8х - 55) = 18 4. 735 : (6х + 17) = 21
8х - 55 = 594 : 18 6х + 17 = 735 : 21
8х - 55 = 33 6х + 17 = 35
8х = 33 + 55 6х = 35 - 17
8х = 88 6х = 18
х = 88 : 8 х = 18 : 6
х = 11 х = 3
корень x^2+y^2+c^2
ab=sqr ((4-2)^2+(11+3)^2+(6-1)^2)=sqr(4+196+25)=15
ac=sqr ( (4-2)^2+(-4+3)^2+(3-1)^2)=sqr(4+1+4)=3
bc=sqr ( (4-4)^2+(-4-11)^2+(3-6)^2) =sqr(0+225+9)=sqr(234)=3*sqr(26)
По теореме косинуса :
bc^2=ac^2+ab^2-2*ac*bc*cos(bac)
234=225+9-2*45cos(bac)
90cos(bac)=0
Косинус равен 0 лишь при 90 (270) градусах, следовательно - угол бас = 90 градусов.