Q. Find the 11 values of x.log2(x+2)+log2(x+6)=5
Combine logarithmic expressions: Apply the product rule of logarithms to combine the two logarithmic expressions.The product rule of logarithms states that logb(a)+logb(c)=logb(a∗c), where b is the base of the logarithms.log2(x+2)+log2(x+6)=log2((x+2)(x+6))
Set equal and rewrite: Set the combined logarithm equal to 5 and rewrite the equation in exponential form.log2((x+2)(x+6))=5 can be rewritten as 25=(x+2)(x+6)
Calculate and expand: Calculate 25 and expand the right side of the equation.25=32(x+2)(x+6)=x2+6x+2x+12x2+8x+12=32
Subtract and solve for x: Subtract 32 from both sides of the equation to set it to zero and solve for x.x2+8x+12−32=0x2+8x−20=0
Factor the quadratic: Factor the quadratic equation.We need to find two numbers that multiply to −20 and add up to 8. These numbers are 10 and −2.(x+10)(x−2)=0
Solve for x: Solve for x by setting each factor equal to zero.x+10=0 or x−2=0x=−10 or x=2
Check for extraneous solutions: Check for extraneous solutions by substituting the values of x back into the original logarithmic equation.For x=−10:log2(−10+2)+log2(−10+6) is undefined because logarithms of negative numbers are not real.For x=2:log2(2+2)+log2(2+6)=log2(4)+log2(8)=2+3=5, which is true.
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