Question

упростить выражение и найти его значение

Answer 1

$1) \: \: \: {(a + 3)}^{2} - (a - 9)(a + 9) = {a}^{2} + 6a + 9 - {a}^{2} + 81 = 6a + 90 = 6 \times ( - 2.5) + 90 = 90- 15 = 75 \\ 2) \: \: \: {(5x - 8)}^{2} - {(4x - 3)}^{2} + 26x = 25 {x}^{2} - 80x + 64 - 16 {x}^{2} + 24x - 9 + 26x = 9 {x}^{2} - 30x + 55 = 9 \times {( - \frac{1}{3} )}^{2} - 30 \times ( - \frac{1}{3} ) + 55 = \frac{9 \times 1}{9} + \frac{30}{3} + 55 = 1 + 10 + 55 = 66$
$3) \: \: \: {(3 {y}^{2} + 4)}^{2} + {(3 {y}^{2} - 4)}^{2} - 2(1 - 3 {y}^{2} )(1 + 3 {y}^{2} ) = 9 {y}^{4} + 24 {y}^{2} + 16 + 9 {y}^{4} - 24 {y}^{2} + 16 - 2(1 - 9 {y}^{4} ) = 18 {y}^{4} + 32 - 2 + 18 {y}^{4} = 36 {y}^{4} + 30 = 36 \times ( \frac{1}{2} ) ^{4} + 30 = \frac{36}{16} + 30 = \frac{9}{4} + 30 = 2 \frac{1}{4} + 30 = 32 \frac{1}{4} = 32.25$