Alvin's age is three times Elgas age. The sum of their ages is 36. What is Elgas age?
1 answer:
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Answer:
The graph of the system of equations solves the equation x + 2 = 2x - 7 ⇒ C
Step-by-step explanation:
<em>Let us revise some important notes about the slope and y-intercept of a line</em>
The form of the linear equation is y = m x + b, where m is the slope and b is the y-intercept
- If the line has a positive slope then its direction will be to the right
- If the line has a negative slope then its direction will be to the left
The y-intercept (0, b) is the the point of intersection between the line and the y-axis
- If the line cuts the y-axis at a point above the x-axis, then b is positive
- If the line cuts the y-axis at a point down the x-axis, then b is negative
<em>To solve our question without any calculation, let us find the direction of the slopes and their y-intercepts</em>
∵ The direction of the blue line is to the left
→ That means m in the equation is negative
∴ Its slope is negative
∵ The line intersects the y-axis at point (0, 2)
→ That means b in the equation = 2
∴ The number in the equation is 2
→ Look at the answer we have two answers have negative slope and
y-intercept 2 in the left hand side ⇒ C and D
∴ The equation of the blue line is represented by the left side x + 2
→ that means the equation of the red line is represented by the right side
∵ The direction of the red line is to the right
→ That means m in the equation is positive
∴ Its slope is positive
→ Only C has a positive slope in the right side
∴ The equation of the red line is represented by 2x - 7
The graph of the system of equations solves the equation x + 2 = 2x - 7
<u><em>Another way:</em></u>
<em>You can solve each equation to find the value of x, then substitute it in one side of the equation to find y , the values of x and y must be (4, 1) as the point of intersection of the two lines in the graph</em>