Printable · GCSE Foundation · ages 14-16

Identities, equivalence and algebraic proof worksheet — GCSE Foundation

Fifteen questions on "identities, equivalence and algebraic proof" — DfE statement A6. Print it, or print three versions so neighbours cannot copy by letter; the key gives the letter for each version.

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Identities, equivalence and algebraic proof worksheet — GCSE Foundation

Maths · GCSE Foundation · A6 · Identities, equivalence and algebraic proof · 15 questions

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1.A student says 4(2x − 3) is equivalent to 8x − 3. Which statement gives the correct verdict and reason?
(a)False — 4(2x − 3) = 8x − 12, not 8x − 3.
(b)True — 4(2x − 3) = 8x − 3 when the bracket is expanded.
(c)False — 4(2x − 3) = 2x − 12, only the −3 is multiplied.
(d)True — 4(2x − 3) = 8x − 3, since both are linear.
2.Which expression is equivalent to 0.5(4x + 6) − x?
(a)3x + 3
(b)2x + 3
(c)x + 3
(d)x + 6
3.A student says that (x + 4)² is equivalent to x² + 16. For which value of x do the two expressions give the SAME result, making it look (misleadingly) like the student could be right?
(a)x = 4
(b)x = −4
(c)x = 0
(d)x = 8
4.Two expressions are 6(x − 1) and 6x − 6. A student says these are equivalent for every value of x. Is the student correct?
(a)Yes, but only when x is a whole number.
(b)No, since 6(x − 1) means 6x − 1.
(c)No, brackets always change an expression's value.
(d)Yes, since expanding 6(x − 1) gives 6x − 6.
5.Which expression is equivalent to 2(x + 6)?
(a)2x + 8
(b)x + 12
(c)2x + 12
(d)2x + 6
6.A student says that 5(x + 2) is equivalent to 5x + 2. Which statement explains why the student is wrong?
(a)Addition must always be done before multiplication, so 5(x + 2) equals 5x + 10 only when x = 0.
(b)The bracket must be worked out first using a value of x, so the two expressions can only be compared once x is known.
(c)The 5 must multiply both terms inside the bracket, so 5(x + 2) expands to 5x + 10, which is never equal to 5x + 2 for any value of x.
(d)5(x + 2) means 5 × x + 2, so the student's answer of 5x + 2 is actually correct.
7.An equation has exactly one value of x that makes it true, but an identity is true for every value of x. Which of these best explains why 3x + 5 = 20 is an equation rather than an identity?
(a)It has an = sign, and equations always use =.
(b)3x + 5 cannot be simplified, so it must be an equation.
(c)Only x = 5 satisfies 3x + 5 = 20, not every value of x.
(d)A number on the right-hand side makes it an equation.
8.Which expression is equivalent to 3(2x − 5) + 4x?
(a)10x + 15
(b)6x − 15
(c)10x − 15
(d)10x − 5
9.Which expression is equivalent to 5x − (x + 3)?
(a)4x + 3
(b)6x − 3
(c)4x − 3
(d)5x − 3
10.Which expression is equivalent to 4(x − 2) + 10?
(a)4x + 2
(b)4x + 8
(c)4x − 8
(d)4x + 18
11.Two expressions are 4(x + 3) and 4x + 3. A student checks whether they are equivalent by substituting x = 2. Which statement correctly interprets the result?
(a)4(x + 3) = 20 and 4x + 3 = 11 when x = 2, so the two expressions are not equivalent, because the bracket means the 3 must be added before multiplying by 4.
(b)4(x + 3) = 11 and 4x + 3 = 11 when x = 2, since the bracket has no effect on the multiplication, so the two expressions are equivalent.
(c)4(x + 3) = 20 and 4x + 3 = 11 when x = 2, but the two expressions are equivalent because both involve the same terms, 4x and 3.
(d)4(x + 3) = 20 and 4x + 3 = 11 when x = 2, so the two expressions are not equivalent, but they would become equal for some larger value of x.
12.Which expression is equivalent to 3(x + 4) − 2(x − 1)?
(a)x + 14
(b)x + 10
(c)5x + 10
(d)x + 13
13.Which of these is an identity?
(a)2(3x + 1) = 6x + 2
(b)5x + 1 = 5(x + 1)
(c)7 − x = x − 7
(d)4x − 3 = 3x + 5
14.A rectangular garden has width w metres and length (w + 3) metres. A gardener writes its perimeter as 2w + 3. Which statement corrects the gardener's mistake?
(a)It is 2(w + (w + 3)) = 4w + 6, not 2w + 3.
(b)It is 3w + 6, since the length doubles but not the width.
(c)It is w + (w + 3) = 2w + 3, matching the gardener.
(d)It is 4(w + 3) = 4w + 12, treating it as a square.
15.Which of these equations is true for every value of x, making it an identity rather than an equation with just one solution?
(a)5x − 3 = 12
(b)2(x + 3) = 2x + 6
(c)x + 7 = 15
(d)3x = x + 10

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