3x = 3 X = 1 b) 7.5x-5x+2 = -450 2 4.5*-5*.5² = -450 5x (7.25)=-450 5x = -450 : 175

Решим уравнение.

b) $$7 \cdot 5^x - 5^{x+2} = -450$$

$$7 \cdot 5^x - 5^x \cdot 5^2 = -450$$

$$7 \cdot 5^x - 5^x \cdot 25 = -450$$

$$5^x (7-25) = -450$$

$$5^x (-18) = -450$$

$$5^x = -450 : (-18)$$

$$5^x = 25$$

$$5^x = 5^2$$

$$x=2$$

Ответ: x = 2