Bài 9: bác an đầu tư 500 triệu đồng vào hai khoản: mua trái phiếu doanh nghiệp với lãi suất 8% một năm và gửi tiết kiệm ngân hàng với lãi suất 6% một năm . Cuối năm bác An nhận được 34 triệu đồng tiền...

To solve this problem, we can use the following steps: Step 1: Set up the equations based on the given information. Let's denote the amount invested in corporate bonds as x million VND and the amount invested in bank savings account as y million VND. The interest earned from corporate bonds is 8% of x: 0.08x The interest earned from bank savings account is 6% of y: 0.06y According to the problem, the total interest earned is 34 million VND: 0.08x + 0.06y = 34 Step 2: Use the fact that bác An invested a total of 500 million VND to set up another equation: x + y = 500 Step 3: Solve the system of equations using substitution or elimination method. Let's solve by substitution method: From equation (2), we have: y = 500 - x Substitute y into equation (1): 0.08x + 0.06(500 - x) = 34 0.08x + 30 - 0.06x = 34 0.02x = 4 x = \frac{4}{0.02} x = 200 Now, substitute x back into equation (2) to find y: 200 + y = 500 y = 500 -200 y=300 So, bác An has invested in corporate bonds with an amount of $$ million VND and in bank savings account with an amount of $$ million VND.