Show that: $(3 x + 7)^{2} - 84 x = (3 x - 7)^{2}$

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Solution

LHS $= (3 x + 7)^{2} - 84 x$

Using , $(a + b)^{2} = a^{2} + 2 a b + b^{2}$

$= (9 x^{2} + 42 x + 49) - 84 x$

$= 9 x^{2} - 42 x + 49$

Using , $(a - b)^{2} = a^{2} - 2 a b + b^{2}$

$= (3 x)^{2} - 2 (3 x) (7) + (7)^{2}$

$= (3 x - 7)^{2} =$ RHS

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Similar questions

Q. Show that

{(3 x + 7)}^{2} - 84 x = {(3 x - 7)}^{2}

prove that:

{(3 x + 7)}^{2} - {(3 x - 7)}^{2} = 84 x

Question 5(i)
Show that:
$(3 x + 7)^{2} - 84 x = (3 x - 7)^{2}$

Question 5(i)
Show that:
$(3 x + 7)^{2} - 84 x = (3 x - 7)^{2}$

Show that :

$(i) {(3 x + 7)}^{2} - 84 x = {(3 x - 7)}^{2}$

$(i i) {(4 p q + 3 q)}^{2} - {(4 p q - 3 q)}^{2} = 48 p q^{2}$

$(i i i) (a - b) (a + b) + (b - c) (b + c) + (c - a) (c + a) = 0$ [3 MARKS]

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Show that: (3x+7)2−84x=(3x−7)2

LHS =(3x+7)2−84xUsing , (a+b)2=a2+2ab+b2=(9x2+42x+49)−84x=9x2−42x+49Using , (a−b)2=a2−2ab+b2=(3x)2−2(3x)(7)+(7)2=(3x−7)2= RHS

Show that: $(3 x + 7)^{2} - 84 x = (3 x - 7)^{2}$

LHS $= (3 x + 7)^{2} - 84 x$

Using , $(a + b)^{2} = a^{2} + 2 a b + b^{2}$

$= (9 x^{2} + 42 x + 49) - 84 x$

$= 9 x^{2} - 42 x + 49$

Using , $(a - b)^{2} = a^{2} - 2 a b + b^{2}$

$= (3 x)^{2} - 2 (3 x) (7) + (7)^{2}$

$= (3 x - 7)^{2} =$ RHS