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Simple Equations

Question
CBSEENMA7000807

Complete the last column of the table.

S. No.

Equation

Value

Say, whether the equation is satisfied. (Yes/No)

(i)

x + 3 = 0

x = 3

(ii)

x + 3 = 0

x = 0

(iii)

x + 3 = 0

x = − 3

(iv)

x − 7 = 1

x = 7

(v)

x − 7 = 1

x = 8

(vi)

5x = 25

x = 0

(vii)

5x = 25

x = 5

(viii)

5x = 25

x = − 5

(ix)

m3=2

m = − 6

(x)

m3=2

m = 0

(xi)

m3=2

m = 6

Solution

(i) x + 3 = 0

L.H.S. = x + 3

By putting x = 3,

L.H.S. = 3 + 3 = 6 ≠ R.H.S.

∴ No, the equation is not satisfied.

(ii) x + 3 = 0

L.H.S. = x + 3

By putting x = 0,

L.H.S. = 0 + 3 = 3 ≠ R.H.S.

∴ No, the equation is not satisfied.

(iii) x + 3 = 0

L.H.S. = x + 3

By putting x = −3,

L.H.S. = − 3 + 3 = 0 = R.H.S.

∴ Yes, the equation is satisfied.

(iv) x − 7 = 1

L.H.S. = x − 7

By putting x = 7,

L.H.S. = 7 − 7 = 0 ≠ R.H.S.

∴ No, the equation is not satisfied.

(v) x − 7 = 1

L.H.S. = x − 7

By putting x = 8,

L.H.S. = 8 − 7 = 1 = R.H.S.

∴ Yes, the equation is satisfied.

(vi) 5= 25

L.H.S. = 5x

By putting x = 0,

L.H.S. = 5 × 0 = 0 ≠ R.H.S.

∴ No, the equation is not satisfied.

(vii) 5= 25

L.H.S. = 5x

By putting x = 5,

L.H.S. = 5 × 5 = 25 = R.H.S.

∴ Yes, the equation is satisfied.

(viii) 5= 25

L.H.S. = 5x

By putting x = −5,

L.H.S. = 5 × (−5) = −25 ≠ R.H.S.

∴ No, the equation is not satisfied.

(ix) m3= 2

L.H.S. = m3

By putting m = −6,

L. H. S. = -63=-2 ≠ R.H.S.

∴No, the equation is not satisfied.

(x) m3= 2

L.H.S. = m3

By putting m = 0,

L.H.S. = 03=0 ≠ R.H.S.

∴No, the equation is not satisfied.

(xi) m3= 2

L.H.S. = m3

By putting m = 6,

L.H.S. = 63=2 = R.H.S.

∴ Yes, the equation is satisfied.

Question
CBSEENMA7000808

Check whether the value given in the brackets is a solution to the given equation or not:

(a) n + 5 = 19 (n = 1) (b) 7n + 5 = 19 (n = − 2)

(c) 7n + 5 = 19 (n = 2) (d) 4p − 3 = 13 (p = 1)

(e) 4p − 3 = 13 (p = − 4) (f) 4p − 3 = 13 (p = 0)

Solution

(a) n + 5 = 19 (n = 1)

Putting n = 1 in L.H.S.,

n + 5 = 1 + 5 = 6 ≠ 19

As L.H.S. ≠ R.H.S.,

Therefore, n = 1 is not a solution of the given equation, n + 5 = 19.

(b) 7n + 5 = 19 (n = −2)

Putting n = −2 in L.H.S.,

7n + 5 = 7 × (−2) + 5 = −14 + 5 = −9 ≠ 19

As L.H.S. ≠ R.H.S.,

Therefore, n = −2 is not a solution of the given equation, 7n + 5 = 19.

(c) 7n + 5 = 19 (n = 2)

Putting n = 2 in L.H.S.,

7n + 5 = 7 × (2) + 5 = 14 + 5 = 19 = R.H.S.

As L.H.S. = R.H.S.,

Therefore, n = 2 is a solution of the given equation, 7n + 5 = 19.

(d) 4− 3 = 13 (p = 1)

Putting p = 1 in L.H.S.,

4− 3 = (4 × 1) − 3 = 1 ≠ 13

As L.H.S ≠ R.H.S.,

Therefore, p = 1 is not a solution of the given equation, 4− 3 = 13.

(e) 4p − 3 = 13 (p = −4)

Putting p = −4 in L.H.S.,

4p − 3 = 4 × (−4) − 3 = − 16 − 3 = −19 ≠ 13

As L.H.S. ≠ R.H.S.,

Therefore, p = −4 is not a solution of the given equation, 4− 3 = 13.

(f) 4− 3 = 13 (p = 0)

Putting p = 0 in L.H.S.,

4p − 3 = (4 × 0) − 3 = −3 ≠ 13

As L.H.S. ≠ R.H.S.,

Therefore, p = 0 is not a solution of the given equation, 4− 3 = 13.

Question
CBSEENMA7000809

Solve the following equations by trial and error method:

(i) 5p + 2 = 17 (ii) 3m − 14 = 4

Solution

(i) 5+ 2 = 17

Putting p = 1 in L.H.S.,

(5 × 1) + 2 = 7 ≠ R.H.S.

Putting p = 2 in L.H.S.,

(5 × 2) + 2 = 10 + 2 = 12 ≠ R.H.S.

Putting p = 3 in L.H.S.,

(5 × 3) + 2 = 17 = R.H.S.

Hence, p = 3 is a solution of the given equation.

(ii) 3m − 14 = 4

Putting m = 4,

(3 × 4) − 14 = −2 ≠ R.H.S.

Putting m = 5,

(3 × 5) − 14 = 1 ≠ R.H.S.

Putting m = 6,

(3 × 6) − 14 = 18 − 14 = 4 = R.H.S.

Hence, m = 6 is a solution of the given equation.

Question
CBSEENMA7000810

Write equations for the following statements:

(i) The sum of numbers x and 4 is 9.

(ii) 2 subtracted from y is 8.

(iii) Ten times a is 70.

(iv) The number b divided by 5 gives 6.

(v) Three-fourth of t is 15.

(vi) Seven times m plus 7 gets you 77.

(vii) One-fourth of a number x minus 4 gives 4.

(viii) If you take away 6 from 6 times y, you get 60.

(ix) If you add 3 to one-third of z, you get 30.

Solution

(i) x + 4 = 9

(ii) − 2 = 8

(iii) 10a = 70

(iv) b5=6

(v) 34t =15

(vi) Seven times of m is 7m.

7m + 7 = 77

(vii) One-fourth of a number x is x4.

x4-4=4

(viii) Six times of y is 6y.

6y − 6 = 60

(ix) One-third of z is z3.

z3+3 = 30