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Which of the equations are true identities?
A. 
(x-2y)^(2)=x^(2)-4xy+4y^(2)
B. 
(m+1)^(2)-m^(2)=1
Choose 1 answer:
(A) Only A
(B) Only B
(C) Both A and B
(D) Neither A nor B

Which of the equations are true identities?\newlineA. (x2y)2=x24xy+4y2 (x-2 y)^{2}=x^{2}-4 x y+4 y^{2} \newlineB. (m+1)2m2=1 (m+1)^{2}-m^{2}=1 \newlineChoose 11 answer:\newline(A) Only A\newline(B) Only B\newline(C) Both A \mathrm{A} and B \mathrm{B} \newline(D) Neither A \mathrm{A} nor B \mathrm{B}

Full solution

Q. Which of the equations are true identities?\newlineA. (x2y)2=x24xy+4y2 (x-2 y)^{2}=x^{2}-4 x y+4 y^{2} \newlineB. (m+1)2m2=1 (m+1)^{2}-m^{2}=1 \newlineChoose 11 answer:\newline(A) Only A\newline(B) Only B\newline(C) Both A \mathrm{A} and B \mathrm{B} \newline(D) Neither A \mathrm{A} nor B \mathrm{B}
  1. Analyze option A: Let's first analyze option A: \newline(x2y)2=x24xy+4y2(x-2y)^{2}=x^{2}-4xy+4y^{2}\newlineWe will use the formula (ab)2=a22ab+b2(a-b)^2 = a^2 - 2ab + b^2 to expand the left side of the equation.
  2. Expand (x2y)2(x-2y)^2: Expanding (x2y)2(x-2y)^2 using the formula:\newline(x2y)2=x22(x)(2y)+(2y)2=x24xy+4y2(x-2y)^2 = x^2 - 2\cdot(x)\cdot(2y) + (2y)^2 = x^2 - 4xy + 4y^2
  3. Compare expanded form with right side: Now let's compare the expanded form with the right side of the equation given in option A:\newlineExpanded form: x24xy+4y2x^2 - 4xy + 4y^2\newlineGiven form: x24xy+4y2x^2 - 4xy + 4y^2\newlineSince both forms are identical, option A is a true identity.
  4. Analyze option B: Next, we analyze option B: \newline(m+1)2m2=1(m+1)^{2}-m^{2}=1\newlineWe will expand (m+1)2(m+1)^2 and then subtract m2m^2 to see if the result equals 11.
  5. Expand (m+1)2(m+1)^2 and subtract m2m^2: Expanding (m+1)2(m+1)^2 using the formula (a+b)2=a2+2ab+b2(a+b)^2 = a^2 + 2ab + b^2:\newline(m+1)2=m2+2m1+12(m+1)^2 = m^2 + 2\cdot m\cdot 1 + 1^2\newline=m2+2m+1= m^2 + 2m + 1
  6. Compare result with 11: Now we subtract m2m^2 from both sides of the expanded form:\newline(m2+2m+1)m2=2m+1(m^2 + 2m + 1) - m^2 = 2m + 1\newlineThis does not equal 11, as the right side of the equation in option B suggests.
  7. Compare result with 11: Now we subtract m2m^2 from both sides of the expanded form:\newline(m2+2m+1)m2=2m+1(m^2 + 2m + 1) - m^2 = 2m + 1\newlineThis does not equal 11, as the right side of the equation in option B suggests. Since the result of the expansion and subtraction in option B does not equal 11, option B is not a true identity.

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