... = 2 0 ,25 0 ,25 0 ,25 1,00 0 ,25 t Vỡ hm s f ( t ) = + 5t ng bin trờn R nờn f ( t1 ) = f ( t2 ) t1 = t2 Mt khỏc 5( x 1) + ( x 1) = 5( x2 x 0 ,25 0 ,25 ) + x2 x f x = f x2 x ( ) ( ( ) ) x = x2 ... 0 ,25 Vỡ cos x sin x nờn : 2sin x + cos x + 2sin x cos x + = t t sin x + cos x = t vi Phng trỡnh tr 0 ,25 0 ,25 0 ,25 0 ,25 ( sin x ) ( 2sin x + cos x + 2sin x cos x + 1) = thnh: t = t + 2t ... x2 + + y ( x + y 2) = y Ta bin i h v dng : Nu y = thỡ h vụ ( x + 1) ( x + y ) = y 0 ,25 0 ,25 0 ,25 1,00 0 ,25 nghim x2 + y + ( y + x 2) = Nu y thỡ ta bin i h v dng x + ( y + x 2) ...