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Figure 2 shows the straight line l_1 with equation 4y = 5x + 12 - Edexcel - A-Level Maths Pure - Question 10 - 2018 - Paper 1

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Figure 2 shows the straight line l_1 with equation 4y = 5x + 12. (a) State the gradient of l_1. (1) The line l_2 is parallel to l_1 and passes through the point E... show full transcript

Worked Solution & Example Answer:Figure 2 shows the straight line l_1 with equation 4y = 5x + 12 - Edexcel - A-Level Maths Pure - Question 10 - 2018 - Paper 1

Step 1

State the gradient of l_1

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Answer

The equation of the line is given as:

4y=5x+124y = 5x + 12

To find the gradient, we first convert this into the slope-intercept form, which is:

y=mx+cy = mx + c

Dividing through by 4 gives:

y=54x+3y = \frac{5}{4}x + 3

Thus, the gradient (m) of the line l_1 is:

m=54m = \frac{5}{4}

Step 2

Find the equation of l_2

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Answer

Since l_2 is parallel to l_1, it will have the same gradient. Therefore, we know that:

m=54m = \frac{5}{4}

Now, we use the point E (12, 5) to find the y-intercept (c). Using the point-slope formula for the line:

yy1=m(xx1)y - y_1 = m(x - x_1)

Substituting in the values gives:

y5=54(x12)y - 5 = \frac{5}{4}(x - 12)

Expanding this, we find the equation of the line l_2:

y=54x5412+5y = \frac{5}{4}x - \frac{5}{4} \cdot 12 + 5

Calculating, we get:

y=54x15+5=54x10y = \frac{5}{4}x - 15 + 5 = \frac{5}{4}x - 10

Step 3

Find the coordinates of (i) the point B

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Answer

To find point B, we set x = 0 in the equation of l_2:

y=54(0)10=10y = \frac{5}{4}(0) - 10 = -10

Thus, the coordinates of point B are:

(0,10)(0, -10)

Step 4

Find the coordinates of (ii) the point C

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Answer

To find point C, we set y = 0 in the equation of l_2:

0=54x100 = \frac{5}{4}x - 10

Rearranging gives:

54x=10\frac{5}{4}x = 10

Multiplying by 45\frac{4}{5} yields:

x=4510=8x = \frac{4}{5} \cdot 10 = 8

Thus, the coordinates of point C are:

(8,0)(8, 0)

Step 5

Find the area of ABCD

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Answer

Since ABCD is a parallelogram, we can calculate its area using the formula:

Area=base×height\text{Area} = \text{base} \times \text{height}

Here, the base AC is length 8, derived from point C (8, 0) to A (0, 0). The height is the vertical distance from point B (0, -10) to the x-axis, which is 10. Thus, the area can be calculated as:

Area=8×10=80\text{Area} = 8 \times 10 = 80

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