A12=a1+(n-1)*d a12=3,1+(12-1)*8,7=98.8
А) (3m + n)(3m - n) = 9m² - n²
б) (x - 4y)(x + 4y) = x² - 16y²
в) (2x - m)² = 4x² - 4xm + m²
г) (2x)² - m² = 4x² - m²
( Х - 1 )/5 = ( 5 - Х )/2 + ( 3х/4 )
<span>4( Х - 1 ) = 10( 5 - Х ) + 15х </span>
<span>4х - 4 = 50 - 10х + 15х </span>
<span>4х - 4 = 50 + 5х </span>
<span>5х - 4х = - 4 - 50 </span>
<span>Х = - 54</span>