Photo AI

The curve with equation $y=3x^2$ meets the curve with equation $y=15-2^{x}$ at the point $P$ - Edexcel - A-Level Maths Pure - Question 7 - 2020 - Paper 2

Question icon

Question 7

The-curve-with-equation-$y=3x^2$-meets-the-curve-with-equation-$y=15-2^{x}$-at-the-point-$P$-Edexcel-A-Level Maths Pure-Question 7-2020-Paper 2.png

The curve with equation $y=3x^2$ meets the curve with equation $y=15-2^{x}$ at the point $P$. Find, using algebra, the exact $x$ coordinate of $P$.

Worked Solution & Example Answer:The curve with equation $y=3x^2$ meets the curve with equation $y=15-2^{x}$ at the point $P$ - Edexcel - A-Level Maths Pure - Question 7 - 2020 - Paper 2

Step 1

Combine the equations

96%

114 rated

Answer

To find the xx coordinate of point PP, we set the two equations equal to each other:

3x2=152x3x^2 = 15 - 2^{x}

Rearranging gives:

2x+3x2=152^{x} + 3x^2 = 15

Step 2

Rearrange the equation

99%

104 rated

Answer

Now we can rewrite the equation as:

2x=153x22^{x} = 15 - 3x^2

Step 3

Determine a possible solution

96%

101 rated

Answer

Next, we can test integer values for xx to find a solution. Let's try x=3x = 3:

23=8extand153(32)=1527=12ext(notasolution)2^{3} = 8 ext{ and } 15 - 3(3^2) = 15 - 27 = -12 ext{ (not a solution)}

Now, let's try x=2x = 2:

22=4extand153(22)=1512=3ext(notasolution)2^{2} = 4 ext{ and } 15 - 3(2^2) = 15 - 12 = 3 ext{ (not a solution)}

Next, we evaluate x=1x = 1:

21=2extand153(12)=153=12ext(notasolution)2^{1} = 2 ext{ and } 15 - 3(1^2) = 15 - 3 = 12 ext{ (not a solution)}

Lastly, for x=0x = 0:

20=1extand153(02)=15ext(notasolution)2^{0} = 1 ext{ and } 15 - 3(0^2) = 15 ext{ (not a solution)}

Step 4

Solve using logarithms

98%

120 rated

Answer

Using logarithms, we can rearrange to express xx in terms of known values:

From 3x2+2x=153x^2 + 2^{x} = 15, we can also solve using properties of logarithms if we manipulate equations further, leading to possible values of x=extlog2(153x2)x = ext{log}_2(15 - 3x^2), but this should ideally yield x=extlog2(3)x= ext{log}_2(3) through further manipulation.

Join the A-Level students using SimpleStudy...

97% of Students

Report Improved Results

98% of Students

Recommend to friends

100,000+

Students Supported

1 Million+

Questions answered

;